MAHARASHTRA, INDIA — In clinics and labs around the world, scientists are uncovering a consequence of air pollution that received little attention for decades: Polluted air not only damages the lungs and heart but also harms the brain.

Large studies conducted in Asia, the United States and Europe have linked long-term exposure to air pollution with a higher risk of depression, anxiety and cognitive decline, while lab- and animal-based studies hint at possible mechanisms driving this effect. Research suggests pollution may also increase the risk of schizophrenia and bipolar disorder, and even suicide risk.

The scale of the problem is staggering, as air pollution affects almost everyone on the planet.

Roughly 99% of the global population breathes air with pollution levels exceeding the World Health Organization's air-quality guidelines, with the most polluted air often found in low- and middle-income countries. In India, where pollution levels are among the highest in the world, these findings may help to explain mental health symptoms that many people have silently experienced for years, scientists told Live Science.

Pollution's mental toll

Areas of India with long-term exposure to high pollution have provided some of the strongest evidence of this link.

A 2025 analysis surveyed 359 people in northern India, finding that residents of communities living within 3 miles (5 kilometers) of coal-fired thermal power plants were more likely to report stress, anxiety and depression than those living farther from these power plants. Women, in particular, were affected.

Notably, people's overall exposure to air pollution sources is also shaped by gender roles. Household air pollution is common in rural homes in India because biomass fuels, such as firewood, dried cow dung cakes, and crop residues, are used for cooking or heating water. In an analysis of nearly 30,000 adults ages 60 and above across India, those using these solid fuels were more likely to report depressive symptoms than those using cleaner cooking methods like electricity or liquefied gas, even after accounting for factors such as economic status, education, health, and living conditions. Women often spend several hours near traditional cooking stoves or other smoke sources each day, thereby intensifying their exposure over that of men who aren't tasked with cooking. A similar pattern has been observed in other Asia-Pacific countries.

That's borne out by the experience of Rukmini Manjare, 54, who lives in Bubnal village in the Indian state of Maharashtra. For many years, she worked outside in the sugarcane fields, where the burning of husks produces a smoky haze.

But unlike the men in her family, she also spends hours cooking over a traditional stove. A decade ago, she started feeling restless and anxious whenever pollution levels spiked.

Recently, Manjare's family tried to reduce her smoke exposure by installing a solar water heater. But smoke from nearby homes still drifts into her house.

"Almost every family uses the traditional stove for at least two hours in the morning daily," she told Live Science.

Worldwide problem

Manjare's experience is a common one across the Indian subcontinent, where nearly the entire population of 1.4 billion people breathes air that exceeds safe pollution limits. In 2023, for instance, the country's average fine particulate pollution, called PM2.5, was about 41 micrograms per cubic meter ‪—‬ more than eight times the level the World Health Organization has deemed safe.

Evidence from other population studies points in a similar direction. In a February analysis of almost 35,000 adults from 12 Indian states, scientists examined the effects of long-term exposure to PM2.5. These tiny particles measure 2.5 micrometers or smaller, meaning they can penetrate deep into the lungs. Living in areas with higher fine-particulate pollution levels, on average, was associated with greater odds of having been diagnosed with depression or anxiety.

This analysis looked at both the average pollution levels in different areas and the composition of that pollution, examining how specific components of PM2.5 were associated with mental health outcomes. Some components of the air pollution — such as carbon-rich molecules and secondary inorganic aerosols, like sulfates, ammonium and nitrates — showed stronger associations with depression and anxiety than others did. Those components better predicted mental health outcomes than total pollutant concentrations alone did.

Treating air pollution as a single, uniform pollutant may therefore "underestimate its mental-health impacts, particularly in countries such as India, where pollution sources and chemical composition vary widely by region and season," said study senior author Sagnik Dey, head of the Centre for Atmospheric Sciences at the Indian Institute of Technology Delhi.

The mental health effects build up over long periods, making them easy to overlook at the individual level. But when millions of people are exposed over decades, "these small effects can add up to a substantial mental health burden at the population level," Dey told Live Science.

India's data on pollution reflects a global pattern. In a December 2025 analysis of health records from 23.7 million older adults in the United States, long-term exposure to PM2.5 was associated with a higher risk of late-life depression. This link persisted even after accounting for factors such as income and education, which can also influence mental health. Similar patterns have been observed in Europe.

When pollution becomes personal

While population-level data identifies broad trends, they may conceal how disabling the symptoms can be for individual people.

Manjare told Live Science that her symptoms of anxiety have worsened over the past decade. Now even minor worries trigger physical symptoms. "Whenever I feel stressed and anxious, my blood pressure shoots up," she said. "I cannot handle even a minute of stress anymore."

The episodes are often accompanied by severe pain in her legs and neck. At times, the only relief comes from a pain-relief injection at the local clinic. "I have now gotten used to it," she said.

Over time, Manjare began noticing a pattern. On days when the air looks hazy and gray and a smell of smoke lingers, her breathing feels a little heavier than usual. On those days, she feels unusually dull and anxious. "There's this sense of constant worry, which I find it difficult to explain," she said.

Part of that anxiety comes from anticipating an episode of pain. But she also says the anxiety emerges on the hazy days before any physical symptoms start.

These changes have taken a toll. She rarely feels like eating. "I love cooking food for everyone, but most of the time, I don't feel like eating it myself," Manjare said. The persistent stress eventually forced her to stop working in the sugarcane fields.

Manjare's worsening symptoms coincide with rising levels of air pollution in the region. Several traditional brick-making kilns operate nearby, and with sugarcane planting nurseries proliferating, farmers frequently burn farm residue, adding another layer of pollution. Vehicles and nearby industries add to this mix, as does smoke from household stoves, where firewood and plastic seedling trays are burned daily to heat water for bathing.

The pollution is visible in everyday life. "If you leave white clothes outside to dry, they turn dark within an hour." On some days, soot settles so quickly inside the house that she sweeps the floor every hour.

After years of living in these conditions, Manjare can often sense when pollution levels have risen, even without checking air-quality readings. "I immediately experience elevated blood pressure, a constant feeling of helplessness, and I stop stepping out of the house," she said.

Around 12 miles (20 kilometers) away, in Jambhali, Maharashtra, more than 100 sugar cane nurseries fill the air with smoke and fine particles — and residents Lalita Koli, 63, and Krishnabai Koli, 65, report similar symptoms.

Koli spent six years working in the sugarcane fields, but she quit because the anxiety, physical symptoms and sense of dread became too much for her.

On heavily polluted days, Koli feels dizzy and develops full-body pain.

After years of living in these conditions, Manjare can often sense when pollution levels have risen, even without checking air-quality readings. "I immediately experience elevated blood pressure, a constant feeling of helplessness, and I stop stepping out of the house," she said.

Around 12 miles (20 kilometers) away, in Jambhali, Maharashtra, more than 100 sugar cane nurseries fill the air with smoke and fine particles — and residents Lalita Koli, 63, and Krishnabai Koli, 65, report similar symptoms.

Koli spent six years working in the sugarcane fields, but she quit because the anxiety, physical symptoms and sense of dread became too much for her.

On heavily polluted days, Koli feels dizzy and develops full-body pain.

"Sometimes I feel like I will die any moment," she said. "I sit and cry, but it's very difficult to explain what is happening to me."

Pollution and the brain at the cellular level

Several biological pathways may help to explain what Manjare and others like her are experiencing. Payel Kundu, a doctoral researcher at the Indian Institute of Technology Delhi, who co-authored the study with Dey, noted that one of the key mechanisms is likely neuroinflammation, a process in which the brain's immune system becomes activated.

PM2.5 is small enough to enter the bloodstream and reach the brain by crossing the blood-brain barrier. The particles can travel directly from the nose to the brain along the olfactory nerve, and they may also indirectly affect the brain via the gut-brain axis, the communication network linking the digestive system and the brain, Kundu told Live Science.

Laboratory studies suggest that when brain cells are directly exposed to fine particulate pollution, they incur damage that impairs their function and triggers cell death. Cell and animal-based studies find that brain tissue responds to pollution by activating its immune defenses, while also producing unstable molecules that damage cells ‪—‬ an effect known as oxidative stress.

While many cell-based studies of inflammation and pollution focus on neurodegenerative diseases or developmental disorders, studies also link neuroinflammation with anxiety and depression.

Certain components of fine particulate pollution, such as carbon-rich particles and secondary inorganic aerosols, seem key to activating the immune and inflammatory pathways in the brain, Kundu said.

PM2.5 may also disrupt the signaling of brain chemicals involved in mood, such as dopamine and norepinephrine. In addition, fine particulate pollution can also interfere with a key component of the body's stress-response system, known as the hypothalamic-pituitary-adrenal axis.

Animal experiments are beginning to show a causal link between polluted air, neuroinflammation and mental health problems. In one study, mice exposed to higher levels of fine particulate pollution — around 185 micrograms per cubic meter showed more depression-like behavior than mice exposed to only 58 micrograms per cubic meter. The high-pollution group moved and explored their surroundings less, and in a water-based stress test, they spent more time floating without trying to escape. In another study, mice exposed to real-world fine particulate pollution for four, six and eight weeks developed depression-like behaviors, alongside changes in inflammatory signaling and in certain signaling pathways involved in neuron growth and function.

Air pollution can also affect mental health indirectly. Wei Jie Seow, an assistant professor at the Saw Swee Hock School of Public Health at the National University of Singapore, said polluted air is already known to contribute to heart and lung diseases. Those physical health problems are closely linked with higher rates of depression and other mental health challenges.

"So part of the mental-health effect may actually be mediated through declining physical health," Seow told Live Science. In a study of more than 17,000 adults ages 45 and older in China, her team found that ozone was tied to the largest increase in depressive symptoms among the pollutants examined.

Ozone, a reactive gas formed when sunlight interacts with pollutants from vehicles and industrial manufacturing, has been linked to inflammation and an increased risk of cardiovascular disease. Cardiovascular conditions, in turn, are associated with a higher risk of depression, suggesting one way such pollution affects mental health.

Despite the growing evidence, scientists say many questions remain. Yang Liu, a professor of environmental health at Emory University in Atlanta whose research has linked air pollution to the risk of depression, said the next step is to better understand how PM2.5 affects depression risk by conducting long-term studies that track people over time while also measuring pollution exposure and signs of brain inflammation.

Another gap lies in understanding how these risks unfold across different populations and environments. Future research needs to focus on long-term studies that follow people over time, especially in low- and middle-income countries, Dey suggested.

It may also need to look beyond pollution. Air pollution rarely occurs in isolation; it often coincides with other environmental pressures, such as extreme heat, noise and social stress, Dey noted. Understanding how these overlapping stressors interact is crucial for designing effective interventions and policies.

No easy solutions

While scientists are still uncovering exactly how polluted air affects the brain, many say the most obvious solution is to clean the air.

"If we reduce pollution at the source, we reduce exposure for everyone simultaneously, including vulnerable populations who may not have the means to protect themselves individually," Seow said.

Population-level policies that curb emissions from transportation, industry and power generation are therefore critical, researchers say. Liu noted that studies have linked improvements air quality with better mental health outcomes, so as air quality improves, so does mental health.

Some scientists say solutions should focus not just on reducing overall pollution levels but also zero in on especially harmful particulates. "Not all PM2.5 particles are equally harmful, so targeted interventions may be more effective than strategies that focus only on reducing overall PM2.5 levels," Dey said.

Reducing emissions of sulfur dioxide, nitrogen oxides and ammonia could limit the formation of secondary particles such as sulfates, nitrates and ammonium, which are more strongly associated with mental health outcomes, Dey said. Cutting emissions from traffic and reducing the burning of biomass for fuel could also reduce exposure to carbon-rich particles, he added.

At the same time, individual and community-level measures can help. Expanding green space and limiting heavy traffic near homes could improve both air quality and psychological well-being, Liu suggested.

Measures such as improving indoor air filtration and avoiding high-exposure environments on heavily polluted days, where possible, also may help, Seow said.

For Manjare, the problem is not just the polluted air, but how easily it goes unseen. “If we could show how pollution levels rise through the day, from daily activities as well as sources like industry, traffic, and crop burning, people would understand how serious it is,” she said.

Editor's Note: This story was supported by Earth Journalism Network as part of the Following the Fumes cross-border collaboration

Cars on the road today are 99% cleaner than they were in 1970. Air quality in the United States is much, much better as a result. In Los Angeles, where I live, lead levels in the air were 50 times higher in the 1970s than today, and the amount of lead in kids’ blood has plummeted.

What made that drop possible is arguably the most important environmental technology ever invented: the catalytic converter.

California has long had the authority under the federal Clean Air Act to set emissions standards for cars and trucks that are higher than the nation's, and its early use of that authority is a major reason why catalytic converters are now standard in vehicles and people are healthier across the country.

At a time when the Trump administration is attacking California's ability to cut air and climate pollution and revoking its Clean Air Act waivers, it's helpful to remember just how important the state's leadership has been in making the air Americans breathe so much healthier.

As I recount in my forthcoming book, "Smog and Sunshine: The Surprising Story of How Los Angeles Cleaned Up Its Air," California's role in the emergence of catalytic technology is often downplayed. The passage of the 1970 Clean Air Act is typically given the credit. That law deserves accolades for its key role. So does William Ruckelshaus, the first administrator of the U.S. Environmental Protection Agency.

But without California's willingness in the early 1970s to push automakers to meet tough standards, the technology would have developed more slowly and the air would have remained dirtier for many more years.

Birth of the catalytic converter

Eugene Houdry invented the first catalytic converter technology in the 1950s. Years earlier, he had developed the Houdry process for catalytic cracking, which makes converting crude oil into gasoline much easier. That invention in the mid-1930s helped spur the mass adoption of cars and trucks in the U.S.

Widespread car ownership altered American life, changing where people lived, worked and vacationed. But cars also brought terrible smog as their use skyrocketed. When Houdry realized his life's work was choking the air of Los Angeles, he decided to do something about it. By the late 1950s, Houdry had invented a rudimentary catalytic converter.

You might think that this invention, which Houdry said could make "the lung cancer curve dip," would lead carmakers to install the technology on their new vehicles.

But that is not what happened. Instead, auto manufacturers engaged in what the government described as a yearslong conspiracy to keep emissions-limiting technology off the market, ultimately leading to an antitrust legal settlement.

It wasn't until the passage of the 1970 Clean Air Act that carmakers got serious about improving upon Houdry's invention for mass market installation.

The Clean Air Act's ambition

The 1970 Clean Air Act is a remarkable piece of legislation. Passed with only one negative vote and signed into law by President Richard Nixon, the act set wildly ambitious goals. They included a requirement that carmakers cut auto pollutants by 90% by 1975.

Congress passed this requirement knowing that the technology to cut emissions wasn't ready for prime time. Houdry's catalytic invention couldn't work with leaded gasoline, and it hadn't been tested in tough conditions, such as freezing cold or sweltering heat.

The Ford Motor Co., with Lee Iacocca as its president, told Congress in 1970, "If such (pollution cuts) are established … the technology as we know it today would not permit us to continue to produce cars after January 1, 1975."

Congress ignored Ford's dire warning and passed the stringent cuts.

Automakers responded with two separate tactics. The first was to gear up — alongside companies like Corning Glass and the Engelhard Company — to develop technology to meet the 90% cuts. Most of their efforts focused on improving the catalytic converter, made more plausible when Engelhard determined that catalytic converters wouldn’t corrode with unleaded gasoline. The EPA's Ruckelshaus ordered gas stations to make unleaded gasoline available as of Jan. 1, 1975.

While the auto companies worked to meet the congressional mandate, they also pressured Congress and the courts to weaken or delay it. The U.S. Court of Appeals for the District of Columbia Circuit obliged, ordering Ruckelshaus to extend the deadline for compliance by a year. Congress eventually extended the deadline to 1981.

But California did not let up.

A gamble that paid off

California has the authority under federal law to issue its own automobile pollution standards, as long as the standards are stronger than federal standards and the state receives a waiver from the EPA. No other state has similar power, but states can adopt California's higher standards.

After the federal appeals court gave carmakers an extra year to comply with the federal rules, California decided it would not let car companies off the hook.

The state asked Ruckelshaus to grant a waiver for California to issue standards tough enough that carmakers would have to install catalytic technology to meet them.

Ruckelshaus faced enormous pressure to deny the waiver, with automakers arguing that the technology was neither effective nor available. But in a hint of the resolve he would later show in refusing Nixon's order to fire Watergate special prosecutor Archibald Cox, Ruckelshaus gave California the go-ahead in 1973, and the state's rules went into effect for the 1975 model year.

He reasoned that doing so would maintain "continued momentum toward installation of (catalyst) systems … while minimizing risks incident to national introduction of a new technology." In other words, California could serve as a guinea pig for the rest of the country by adopting tough standards.

The gamble paid off. Since California was the nation's largest auto market, companies had strong economic incentives to change their models to meet the state’s standards. Catalytic technology is now not only standard on American vehicles but also on vehicles around the world, and air quality in the U.S. is vastly improved.

With the adoption of the catalytic converter, leaded gasoline was banned and eventually phased out, and lead levels began to drop almost immediately.

Continuing California's legacy

Catalytic converters have removed 8 billion tons of pollution from the air in the U.S. They have saved hundreds of thousands of lives and led to the removal of a deadly neurotoxin, lead, from the atmosphere.

California's standards have spurred important technological innovations for vehicles, including new types of less-polluting gasoline and vehicles that emit no pollution at all.

But the state's ability to set higher standards is under attack. Congress — at the behest of the Trump administration — has overturned three waivers the state was granted to cut even more pollutants and the greenhouse gases that cause climate change. The Trump administration has also sued California to invalidate its mandates for automakers to sell zero-emissions vehicles.

Today, California officials are searching for alternative ways to continue to make cars and trucks cleaner. The state has set aside money to replace federal tax incentives for electric vehicles, and the Legislature is exploring creative ways to hold indirect sources of emissions, such as rail yards, ports and warehouses where vehicles are constantly running, accountable for air pollution.

But these alternatives aren't as powerful as the authority to exceed federal standards to make the air cleaner.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

China's significant reduction in air pollution may have had unexpected benefits in the Arctic: A new study shows that it diminished storms fueled by aerosols and, in turn, reduced sea ice loss. However, at the same time, this huge drop in aerosols may have accelerated global warming, experts say.

"The Chinese people suffered under bad air quality for decades," Bjørn Samset, a senior researcher at the CICERO Centre for International Climate Research in Norway, told Live Science. "This pollution temporarily slowed global warming and gave the rest of us a bit more time to adapt to a warmer climate. What is happening now is that we're seeing the full effects of greenhouse-gas-driven warming, which we would sooner or later have to face anyway."

In late January 2019, wind patterns over the North Pacific shifted, and a series of five powerful cyclones swept into the Bering Sea in rapid succession. Each one drove warm southerly winds across the ice, breaking it apart and pushing it northward. Air temperatures across the northern Bering Sea ran 21.6 to 28.8 degrees Fahrenheit (12 to 16 degrees Celsius) above normal. By early March, ice cover had shrunk by 82%. This represented a retreat of about 154,440 square miles (400,000 square kilometers) — the largest decline ever recorded by satellites at that time of the year.

Scientists have long known that cyclones can devastate Arctic sea ice. What they've been less sure about is what sends those storms there in the first place.

The new study, published March 18 in journal npj Climate and Atmospheric Science, offers an unexpected answer: From 2000 to 2014, smog billowing from Chinese smokestacks may have been steering winter storms northward across the North Pacific, funneling more of them into the Arctic and destroying ice in the Bering Sea.

To understand how soot and sulfate particles over Shanghai could influence ice off the coast of Alaska, it helps to think about what happens inside a storm. Every mid-latitude cyclone — the swirling, comma-shaped systems that generate much of the Northern Hemisphere's winter weather — runs on a kind of heat engine. Warm, moist air evaporates near the ocean surface, rises and condenses into clouds, releasing heat that fuels the storm's circulation.

Aerosols — the tiny particles that make up industrial haze — disrupt this engine in a subtle-but-consequential way. Water vapor normally condenses around a relatively small number of particles, forming large droplets that fall quickly as rain on the storm's southern flank. If the air is full of aerosols, however, each particle becomes a seed for a cloud droplet. The result is a vast number of smaller droplets that don't readily coalesce into raindrops. Rainfall on the storm’s southern flank is suppressed, and moisture travels farther along the storm's conveyor belt toward its northeastern flank, where it releases its heat — in exactly the right place to nudge the whole system poleward.

Lead author Dianbin Cao, a researcher at the Chinese Academy of Sciences' Institute of Tibetan Plateau Research, and colleagues combined four decades of observational data with climate model simulations to examine how aerosol levels over East Asia influenced winter cyclone tracks across the North Pacific. Comparing 14 years of elevated aerosol loading between 2000 and 2014 against 15 lower-aerosol years from the preceding decades, the researchers found that cyclone tracks shifted northward by up to 1.23 degrees by the time the storms dissipated — enough to nearly double the number of cyclones crossing into the Arctic.

This aerosol-driven push on storm systems is "stronger than I might have suspected," said Alex Crawford, an Arctic climate scientist at the University of Manitoba who studies cyclone-sea ice interactions but was not involved in the study. "They've done a really good job of demonstrating the mechanism by which aerosols can impact extratropical cyclones."

When these storms arrive in the Bering Sea, their effects can be dramatic. A cyclone's counterclockwise winds shove ice back toward the Chukchi Sea, between Alaska and Russia. Waves break ice floes apart. Southerly gales bring warmer air that can, even in the depths of winter, tip temperatures above freezing, as happened so acutely in 2019.

There is a potential silver lining, however. China's air pollution cleanup, launched in 2013, has proved to be one of the most effective environmental interventions in history, slashing the country's sulfate aerosol emissions by roughly 75% in about a decade. The study suggests this reduction "could potentially mitigate the poleward migration of the storm track driven by global warming" — sparing the Arctic some of the damage from extratropical cyclones.

But the bigger picture is more complicated. Aerosols also cool the planet by reflecting solar radiation back into space and by making clouds brighter. As they disappear, their cooling effects vanish too, thereby unmasking decades of suppressed greenhouse gas warming. A 2025 study led by Samset, who was not involved in the new study, found that East Asian aerosol reductions have measurably accelerated global warming.

The same aerosol reductions that may ease the cyclone-driven pressure on the Bering Sea are simultaneously unmasking the full effects of global warming.

What this climatic tug-of-war will mean for Arctic sea ice remains to be seen, but Dan Westervelt, an atmospheric scientist at Columbia University’s Lamont-Doherty Earth Observatory and a co-author on Samset’s 2025 study, thinks the warming effect will win out. "Unmasking warming will probably dominate, as it is more persistent and can occur during all seasons, while the storm-track changes are probably more episodic,” he told Live Science.

Westervelt said the study indicates that aerosols exert a greater and more complicated influence on Earth's climate than previously appreciated. "The speed of the aerosol reductions in East Asia is underappreciated," he said. "Emissions decreases that took three decades in North America and Europe are taking one decade in East Asia. What impact this has on cyclones and Arctic warming is going to be really interesting to study, and critical for climate mitigation and adaptation."

MAHARASHTRA, INDIA — When Babytai Suryavanshi first noticed a few scaly patches on her right forearm, she ignored them for three months, thinking it was an infection that would heal on its own.

While working in the sorghum fields last year, she noticed the patches had become more raised and red and that they burned.

A doctor diagnosed her with psoriasis, a condition in which the immune system causes skin cells to grow too quickly, resulting in thick, scaly and sometimes itchy patches that often appear on the elbows, knees, scalp, lower back, palms and feet. Although there's no cure for psoriasis, it can be managed with treatments that suppress parts of the immune system or slow skin growth.

What 76-year-old Suryavanshi didn't know, and what researchers are now uncovering, is that air pollution can play a role in triggering and worsening this disease.

Around 99% of the world's population is exposed to air that doesn't meet the World Health Organization's air quality guidelines. And in 2021, 42.98 million people had a diagnosed case of psoriasis. But studies suggest many people may go undiagnosed in part because it's easily mistaken for other conditions and more difficult to spot on darker skin tones; some estimates suggest 125 million people are affected globally.

For Suryavanshi, the link between her skin condition and pollution became clear after the doctor asked her to pay attention to her environment. For over 30 years, she worked at a sugarcane planting nursery near her home in Jambhali village in Western India. She quit last year because the constant smoke from burning sugarcane residue and plastic seedling trays was triggering repeat flareups, she said. Now, she works on farms, but that also carries risks because nearby factories often expose her to polluted air.

An emerging link

Air pollution is a term that encompasses a wide variety of chemicals and particles that humans spew into the air through industrial activities, from running factories to driving cars. It can encompass everything from wildfire smoke to smog. It contains fine particulate matter of various sizes — including PM2.5, which is smaller than 2.5 micrometers (PM2.5), and PM10, smaller than 10 micrometers — as well as chemicals like nitrogen dioxide (NO2) and nitrogen oxides (NOX).

Psoriasis, meanwhile, is an autoimmune condition in which the immune system attacks the body's own tissues, namely skin cells. People usually have flareups of the condition, which are treated with creams, phototherapy or medicines that calm the immune response. The condition tends to run in families, so there is a genetic component that makes people more vulnerable.

But genes aren't the only factor at play. The link between psoriasis and pollution has been found in several studies from around the world.

For instance, one analysis included nearly 285,000 people from the U.K. Biobank, a repository of health data and biological samples from U.K. adults, who were followed for 15 years. It revealed that long-term exposure to pollution may accelerate biological aging. They measured this aging using the PhenoAge algorithm, a tool known as an "aging clock" that estimates the body's biological age, rather than just the number of years lived. This estimate indicates whether the body is aging faster or slower than an average, healthy baseline, and can also predict the risk of death from any cause or incidence of age-related diseases, like cancer.

Increases in this aging metric were tied to an increased risk of psoriasis, with each one-year increase in biological age tied to a 5% higher risk of the condition.

Another study, from Verona, Italy, found a temporal link between high-pollution days and psoriasis flareups. The study tracked pollution levels in the city in the days leading up to patients visiting the clinic to get treatment for psoriasis, taking an average of the pollution levels over the prior 60 days. The results showed that high exposure to air pollution in that timeframe, defined as passing a certain threshold of PM2.5 and PM10, increased the odds of visits for these flare-ups.

Furthermore, a 2024 study of more than 3,600 Americans investigated the relationship between psoriasis and urinary polycyclic aromatic hydrocarbon (PAH) metabolites, components of air pollution formed during the burning of coal and oil, garbage and other carbon-based substances. People with higher PAH metabolite levels — indicating higher exposure in recent days — were 83% more likely to have psoriasis. Another U.S. based study, published in 2023, linked clinical visits for psoriasis to pollution caused by wildfire smoke.

Even short spikes in pollution may raise the risk of psoriasis-related medical visits. A five-year evaluation in Nanchang, China looked at levels of several pollutants, including nitrogen dioxide and carbon monoxide, and found a linear relationship between rises in pollutant levels and psoriasis-related visits to the doctor. The degree of increased risk and the lag-time between exposure and an outpatient visit varied depending on the specific pollutant being measured, but the lag was typically on the order of a few days to a week.

Causes unraveled

These studies point to some sort of link between pollution and psoriasis, but scientists are now probing deeper into exactly how polluted air triggers or worsens the condition. And the answers, while complex, are beginning to emerge.

Some studies suggest small particles in pollution may directly damage the outside barrier to the body, disrupting the skin both physically and chemically, Dr. Nidhi Singh, an environmental epidemiologist and postdoctoral researcher at IUF–Leibniz Research Institute for Environmental Medicine in Germany, told Live Science in an email.

For instance, it's been shown that fine particulates cause changes to proteins and fats in the skin, said Singh, who authored a paper on genetic and environmental risk factors for psoriasis. These changes may disrupt enzymes in the body's antioxidant defense system, which cleans up tissue damage caused by free radicals, such as reactive oxygen and nitrogen species. It's also possible that air pollution fuels increased production of reactive nitrogen species in human tissue, specifically in skin, Singh added.

Dr. Paolo Gisondi, an associate professor of dermatology at the University of Verona who co-authored the Italian study, told Live Science that while the exact biological mechanism is not fully understood, "we can speculate that air pollutants trigger inflammation in the skin by activating immune cells and driving the release of inflammatory molecules." This abnormal immune activation may then lead to psoriasis.

Singh also noted that, in lab dishes with stem cells that are developing into skin cells, ultrafine particles — the tiniest component of air pollution measuring less than 0.1 micrometer each — can increase the activity of genes associated with inflammation and psoriasis. In lab dishes, ultrafine particles can also disrupt the normal development of keratinocytes, the main cells in the outer skin layer.

A paper published this year looked at U.K. Biobank data and pinpointed a specific gene that may be involved in the mechanism: ZMIZI. This gene typically helps regulate the immune system and inflammation and air pollution is tied to changes in its activity. ZMIZ1 acts as a dial, fine-tuning inflammation levels. However, air pollution can keep this dial locked in the "high" position, causing inflammation to ramp up and increasing the likelihood of autoimmune diseases like psoriasis, the study found.

What can be done?

At an individual level, people can reduce their pollution exposure by staying indoors on high-pollution days and using air purifiers, Singh said. And if they have to go outside, they can try to limit how many of these small particles penetrate their skin and hair follicles by covering exposed body parts with protective clothing. They can also regularly cleanse or exfoliate with products that remove particle buildup from the skin, Singh added.

But Singh emphasized the need for broader regulatory action. In addition to passing rules that reduce air pollution, governments should develop stronger early warning systems for high-pollution days, which can help people know when to stay indoors.

For residents like Suryavanshi, taking steps to avoid her psoriasis triggers is challenging.

There are more than 100 small and large sugarcane nurseries in their village, each of which produces pollution, she said. Like others in her neighborhood, she also heats water for bathing every day on a wood-burning stove, which exposes her to additional smoke pollution.

Last month, her husband, 78-year-old Mahadev Suryavanshi, was also diagnosed with psoriasis, but they can't afford to pay for treatment right now. Each day, he endures a burning and itching sensation on his face that never subsides.

"It's got something to do with the polluted air," he speculated.

Even brief exposure to air pollution may alter the structure of the placenta and push the organ into an inflammatory state, recent laboratory research finds.

Scientists already knew that particles found in air pollution can reach the placenta and get taken up by immune cells there.

"There's no doubt that particles are entering the bloodstream and then accumulating, or getting to, the placenta and being taken up by placental cells," said Dr. Jonathan Grigg, a professor of pediatric respiratory and environmental medicine at Queen Mary University of London who was not involved in the recent study.

The new work added to this understanding by zooming in on special immune cells of the placenta — called Hofbauer cells — to see how their function changed after they were exposed to compounds found in real air pollution.

"I think that this is an important step in filling in the gap between what we know from epidemiological studies," Grigg said.

Those studies pointed to links between exposure to pollutants during pregnancy and the risk of the blood-pressure disorder preeclampsia, for instance. Preeclampsia is tied to poor blood flow to the placenta, and thus low oxygen in the organ. Some researchers argue that placental dysfunction is the root of preeclampsia, but not everyone agrees, as some point instead to the maternal cardiovascular system. But nonetheless, the placenta is thought to be a key factor in the disease.

The recent research, published online in March in the Journal of Environmental Sciences, will also run in the journal's February 2026 print issue. It used what's known as "ex vivo dual placental perfusion," which means the scientists collected full-term placentas from volunteers who donated them at the time of birth, either via cesarean section or vaginal delivery. In all, 13 healthy placentas were donated.

Related: Lab-grown mini-placentas reveal clue to why pregnancy complications happen

"You can't really expose women to air pollution as an experiment," study co-author Dr. Stefan Hansson, a professor of obstetrics and gynecology and a senior consultant in obstetrics at Lund University in Sweden, told Live Science. "So the best model, then, is the placenta perfusion system that we used."

After birth, the placentas are connected to an artificial perfusion system that mimics elements of the female reproductive system. "Within 30 minutes, you hook it up in an artificial womb and uterus," Hansson explained. Tubes connected to one side of the placenta represent the maternal circulatory system, while tubes on the other stand in for the umbilical cord that would connect to the fetus.

Tubes feed nutrients and oxygen to the placentas, keeping them healthy for about six hours and mimicking both the maternal and fetal sides of the organ. Meanwhile, scientists can monitor the organ's metabolism, homeostasis, blood-pressure levels and the behavior of its immune cells.

"That's a good thing in the sense it's covering perhaps the more complex interactions between cells, how fluid and particles are moving through cells," Grigg said. By comparison, studying individual placental cells in a lab dish is arguably less realistic.

The researchers then introduced air pollutants into the system to see what happened. Six placentas were left unexposed to pollution, to serve as a comparison; five were exposed to pollution for five hours; one was exposed for 60 minutes; and one was exposed for 30 minutes. Tissues and fluids were sampled from the system before, during and after these perfusions.

The pollutants themselves were drawn from a previous sampling of air pollution in Malmö, Sweden taken in spring 2017. The samples were collected at a street crossing that sees an annual average traffic density of about 28,000 vehicles. The team focused on "fine" particulate matter, or PM2.5, which includes particles smaller than 2.5 micrometers.

On that point, Grigg told Live Science that "the concentrations of particles that they're using in the perfusates are almost certainly very much higher than the very small concentrations that are going around the body," based on previous research. So there's a question about whether the doses they've tested closely reflect real life. "I think that's probably a valid limitation for this," he said.

Related: Canada's 2023 wildfires contributed to 87,000 early deaths worldwide, study estimates

Nonetheless, at the concentrations tested, the pollutants had a clear effect on the placentas. Even when exposed for only 30 minutes, the placentas showed distinct changes in their collagen, a structural protein that helps organize the tissue. The collagen appeared looser and "disrupted" compared with the dense, organized collagen of the unexposed tissues.

The team also noted that, after an hour of exposure, the placentas started making more human chorionic gonadotropin (hCG), a hormone that peaks in the first trimester and helps maintain the uterine lining. However, high levels of the hormone in the second trimester have been tied to a higher risk of preeclampsia, studies suggest. The new study hints that air pollution may be a factor that drives up hCG levels, though that idea needs to be confirmed.

Meanwhile, the Hofbauer cells of the exposed placentas had a "visible activated appearance" and had shifted into an inflammatory state. In a healthy placenta, the cells are typically biased toward an anti-inflammatory state, but in the context of preeclampsia, they tend to shift in the other direction, the researchers noted in their report.

"This is, of course, an artificial setup and you're exposed for a couple of hours," Hansson noted. You can extrapolate and assume that, in a full-term pregnancy, these harmful effects might accumulate, he said. But as it stands, the placental perfusion system can't directly capture the effects of such long-term exposure, and it also looks only at full-term placentas, not at those in earlier stages of development.

It stands to reason, though, that "if it's happening all the time, then that's going to be clinically relevant," Grigg said.

The results hint that if the inflammation driven by the Hofbauer cells could be subdued with a drug, that may help ward off one factor contributing to preeclampsia in polluted areas, Hansson suggested. That idea remains to be tested in trials, though, and inflammation isn't the only feature of preeclampsia.

What's more, a more effective intervention would be to reduce particulate matter in the air, Grigg said. "We should be reducing exposure to PM2.5; you don't need any more information about that [to justify taking action]," he said.

Grigg also cautioned that the new results don't necessarily point to precautions that individual pregnant people should take.

"I sort of hesitate to say, 'Well, pregnant women have to do something different to protect themselves,'" he said. "There are enough things that pregnant women have to do rather than thinking about how they move around the city."

This article is for informational purposes only and is not meant to offer medical advice.

Satellites recently snapped a giant cloud of "Saharan dust" blowing out to sea from the world's largest hot desert. The hazy mass later traveled more than 4,000 miles (6,500 kilometers) to North America, where it polluted the skies of Florida and other states.

In the early hours of May 28, 2025, a large cloud of dust and sand began to blow out from the Sahara and over the Atlantic Ocean, according to a statement from the National Oceanic and Atmospheric Administration (NOAA). Around a week later, on June 4, the cloud made landfall in Florida, with the plume also reaching Louisiana, Texas and other parts of the Gulf Coast. En route, it also briefly filled the skies of several Caribbean nations, including Puerto Rico and the Bahamas.

A photo captured by the GOES-19 satellite, which is co-run by NASA and NOAA, revealed the cloud as it first began its transatlantic journey. At the time, it covered an area of roughly 240,000 square miles (620,000 square km) between Cabo Verde — an archipelago of 10 volcanic islands in the mid-Atlantic — and the coast of West Africa, including the shorelines of Mauritania, Senegal, Gambia and Guinea-Bissau.

The dust cloud was a "particularly robust, comma-shaped plume," representatives from the Cooperative Institute for Research in the Atmosphere (CIRA) at Colorado State University wrote on Bluesky. However, soon after the photo was taken, the cloud dispersed, making it "appear larger in size."

Astronauts on board the International Space Station (ISS) also captured shots of the plume as it moved across the Atlantic, Live Science's sister site Space.com reported.

Related: See all the best images of Earth from space

In Florida, the plume caused a brief reduction in air quality that may have impacted people with respiratory conditions. The state's skies remained hazy for around 48 hours before the majority of the dust settled — some of which was later visible on windows and cars.

A second, smaller plume reached the U.S. between June 13 and 15.

Saharan dust can have several other surprising effects. "When it reaches the U.S., it can cause hazy skies as well as vivid sunrises and sunsets as the sun's rays scatter the dust in the atmosphere," NOAA representatives wrote. "It can even suppress thunderstorm development over locations where the dust is especially thick."

Dust plumes

Saharan dust gets whipped up by strong gusts of wind, which occur much more frequently in deserts than other environments, and can reach several miles above Earth's surface, according to the U.K. Met Office. This mainly happens between late spring and early fall.

Once the dust is airborne, it hovers above the desert in a region known as the "Saharan Air Layer" — a roughly 2.5-mile-wide (4 km) band of very dry air that forms around 1 mile (1.6 km) above the Sahara desert. Every three to five days, the accumulated dust gets blown out to sea, and if there is enough of it, the particulates form large plumes that can travel across entire oceans, according to NOAA's Atlantic Oceanographic and Meteorological Laboratory, which helps monitor the Saharan Air Layer.

Saharan dust plumes of various sizes reach the U.S. every year, usually peaking in intensity between June and August.

One of the most famous examples in recent years was the "Godzilla" plume, which hit large parts of the southern U.S. in June 2020. During this two-week-long event, the amount of dust reached the highest levels since satellites began tracking plumes 18 years previously, according to a 2021 study.

Exposure to higher-than-average levels of outdoor air pollution and extreme temperatures raises the risk of a prolonged pregnancy, new research suggests.

An analysis of almost 400,000 live births in Australia has revealed that people who were exposed to very hot or cold temperatures, as well as to elevated levels of fine particulate air pollution (PM2.5), during pregnancy were more likely to give birth after 41 weeks compared with people who were not exposed to those conditions.

The average pregnancy normally lasts approximately 40 weeks, while babies who are born after 41 or 42 weeks are referred to as "late-term" or "post-term" births, respectively. Birth delays can increase the risk of birth complications associated with babies being excessively large — including vaginal bleeding or hemorrhage during delivery — as well as the likelihood of stillbirth or death after birth.

The scientists who conducted the new research described their findings in a paper published Jan. 31 in the journal Urban Climate. They claim to be the first to investigate how climate change may affect the risk of prolonged pregnancy.

Related: 'Dengue is coming': Climate-fueled rise in cases will affect the US, scientists warn

"We know that being 'born too soon' — preterm birth — has well-documented health risks, but little attention has been given to the risks associated with being 'born too late'," lead study author Sylvester Dodzi Nyadanu, a research associate in environmental health at Curtin University in Australia, said in a statement.

In the new study, the researchers examined how much PM2.5 air pollution 393,384 people were exposed to monthly shortly before and during pregnancy, from three months before conception to when they gave birth, based on where they lived. During the same time period, they also used a metric known as the Universal Thermal Climate Index (UTCI) to estimate how much thermal stress their bodies were under because of the weather, factoring in elements such as air temperature and humidity.

Overall, they found that 12% — or 47,380 — of the mothers had a prolonged pregnancy (meaning 41 weeks or more) and that higher levels of exposure to PM2.5 and thermal stress measured by the UTCI increased the odds of this happening. This was after they considered other factors that can influence pregnancy duration, such as smoking, socioeconomic status, race and ethnicity, and maternal age. People giving birth for the first time, people over 35, and people living in urban areas were particularly vulnerable to these effects.

Exposure to extreme temperatures and air pollution may prolong pregnancy in numerous ways, the researchers said. For example, both factors may increase the production of unstable molecules called "reactive oxygen species" which can disrupt hormonal function.

Such risks may become more apparent as climate change increases the number of extreme weather events and reduces air quality, Nyadanu said in the statement.

"This study highlights the need for targeted policies and preventative measures to reduce climate-related health risks, including better air quality regulations and public health initiatives aimed at protecting expectant mothers and children from extreme climatic conditions," he added.

This article is for informational purposes only and is not meant to offer medical advice.

Wildfires are becoming more frequent, extreme and destructive in the United States, especially in western states like California.

California has been contending with longer and more active fire seasons in recent years — in 2023, more than 7,000 wildfires occurred in the state, with the California Department of Forestry and Fire Protection having to respond to approximately 590,000 associated emergencies. In January 2025, a devastating fire swept through Los Angeles County, affecting nearly 40,000 acres (16,000 hectares) in its first nine days. The event became the second-deadliest wildfire in California history, claiming 30 lives.

Major wildfires leave a trail of destruction in their wake, putting people's lives at risk and forcing them to quickly evacuate their homes and businesses. Climate change is a major factor worsening these disasters, and it's expected to continue to worsen the situation in coming years.

One major health risk posed by wildfires is the smoke they let off. Wildfire smoke can have many harmful effects on the body, including on the lungs, heart and brain. Thankfully, there are certain measures that people can take to protect themselves, experts told Live Science.

Related: What's in the pink fire retardant being dropped on LA, and is it dangerous?

How does wildfire smoke affect the body?

Wildfire smoke contains a multitude of different chemicals that form as things burn, Sara Adar, a professor of epidemiology at the University of Michigan, told Live Science.

Among the most concerning substances are tiny particles collectively known as particulate matter 2.5 (PM2.5). These particles are less than 2.5 micrometers in size — roughly 28 times smaller than the width of a human hair — and they can become trapped in the inner linings of the nose, mouth and eyes.

In the short term, this triggers irritation and other symptoms, such as burning eyes, a runny nose or cough, which can set in immediately after exposure. People with skin conditions like eczema may also be more likely to experience flare-ups of their condition as a result of short-term exposure to PM2.5 during a wildfire.

On longer scales, these particles are small enough to be inhaled into the lungs and cause additional harm to the body, especially as they are absorbed into the bloodstream. For example, they may trigger inflammation that aggravates respiratory conditions, such as asthma or chronic obstructive pulmonary disease (COPD). This may occur right away or within a day or two of exposure to wildfire smoke, Dr. Stephanie Lovinsky-Desir, an assistant professor of pediatrics in environmental health sciences at Columbia University in New York, told Live Science.

People with these respiratory conditions may find it harder to breathe because of high levels of exposure to PM2.5 and in urgent cases, need to go to the hospital, Adar said. Studies have shown that PM2.5 can also irritate the heart via the bloodstream, leading to an increased risk of emergency department visits for heart attacks and coronary heart disease within 24 hours of exposure to dense wildfire smoke.

PM2.5 may also affect various aspects of cognition, such as memory, attention and learning, potentially by inducing inflammation in the central nervous system and impeding communication between neurons.

Research has also shown that long-term exposure to wildfire smoke — namely over a period of three years — is associated with an increased risk of developing dementia. In addition, more than two weeks of exposure to heavy smoke may make people more likely to report various mental health symptoms, such as anxiety and depression, according to a study of wildfires in Oregon.

How can people protect themselves from wildfire smoke?

The first thing that people can do to protect themselves from wildfire smoke is to avoid exposure to it as much as possible, Lovinsky-Desir said.

That means leaving the area if you're in an evacuation zone, staying indoors as much as possible with the windows closed, and if you're travelling in a car, keeping your windows up, she explained. Running air purifiers, such as those with filters that can handle fine particles, inside the home can also be helpful, she said. If you don't have a filter, standard air conditioning can also help, she added.

People who have underlying lung disease or care for people who do should ensure that they have the necessary medications on hand to avoid being stranded without them in an emergency, Lovinsky-Desir said.

If you wish to exercise on days where air pollution levels are high, it may be better to do so indoors, such as at a gym, Adar said. And if you must be outside for any reason, wearing a face mask can help mitigate the risk of health impacts from pollutant exposure, she added. N95 respirators can reduce PM2.5 exposure if used correctly, for example. A key thing is to have the mask snugly fitted against your face; the California Department of Health provides tips on how to do that.

This article is for informational purposes only and is not meant to offer medical advice.

South America is experiencing record-breaking fires, which have led to "black rain," green rivers and hazardous air pollution almost 50 times higher than the level recommended by the World Health Organization, according to the air quality monitoring company IQair.

Between Jan. 1 and Sept. 16, the continent recorded 364,485 forest fires, surpassing the 2007 record of 345,322 fires, according to data from the Brazilian Space Research Institute and Reuters.

The historic drought in the Amazon has worsened the spread of the fires. Many of the fires have been attributed to human activity, but the drought has created favorable conditions for their rapid spread. As a result, 60% of Brazil's territory is currently affected by smoke.

Including neighboring countries and the Atlantic Ocean, the area impacted by the toxic cloud now spans 4 million square miles (10 million square kilometers) — an area larger than the entire United States.

"The air quality in Brazil has never been worse," Alessandra Fidelis, a researcher at the Plant Ecology Laboratory of the State University of São Paulo, told Live Science.

Natalia Gil, an atmospheric science expert and member of the Air Quality and Emissions Department at the Technological Laboratory of Uruguay, told Live Science there has been a progressive decline in air quality in cities across southern Brazil, northern Argentina, Bolivia, Paraguay and northeastern Uruguay.

Related: Sahara desert hit by extraordinary rainfall event that could mess with this year's hurricane season

In recent weeks, Gil observed "a significant increase" in black carbon, particulate matter and gases such as ozone, nitrogen oxides and carbon monoxide in cities as far-flung as Buenos Aires, São Paulo, Londrina, Rio de Janeiro, Cochabamba and La Paz. In Uruguay's capital, Montevideo, residents experienced poor visibility for several days due to the dense smoke cloud and black rain — precipitation that turns dark due to the mixture of ash and soot — recorded in multiple parts of the country. The same situation occurred across 11 Argentine provinces, including the Metropolitan Area of Buenos Aires.

In São Paulo, meanwhile, the Pinheiros River turned emerald green due to an algae bloom triggered by the severe drought.

Paulo Saldiva, a pathologist and professor at the University of São Paulo School of Medicine, compared the smoke produced by burning biomass to cigarette smoke, noting that both contain toxic substances that enter the body through the eyes, respiratory tract and lungs. In a metropolis like São Paulo, for example, the level of vehicular and industrial pollution is equivalent to smoking four to five cigarettes daily. However, for those exposed to smoke from forest fires over long periods, the impact is akin to "lighting one cigarette after another," Saldiva said.

Environmental changes in recent decades, along with shifts in land use, have significantly altered fire regimes. While Brazil has always experienced dry seasons, the average number of consecutive rainless days has increased from 80 to 100 in the last decade, indicating a worsening of climate-related impacts, Fidelis noted. "The forest is more susceptible to burning, even with the reduction in deforestation rates. It has become more flammable," Fidelis said.

In addition to changes in precipitation, rising temperatures, soil moisture and carbon dioxide levels can influence the timing, extent, duration, frequency and intensity of fires, Luis López-Mársico, a researcher at the Institute of Ecology and Environmental Sciences at the University of the Republic of Uruguay, told Live Science.

In much of Brazil, these changes manifest as higher temperatures, reduced rainfall, and, most notably, an increase in extreme drought events, which prolong the so-called "fire seasons,"

All of this constitutes a "new normal," according to Fidelis. "We need to start recognizing that we are dealing with a new factor we once thought of as a future scenario, but which is now our reality: climate change," she said.

Roughly one in six people are affected by infertility worldwide.

And with more than half the world's population now living in urban areas, researchers are interested in whether living in noisy and polluted cities could be to blame.

A new study in Denmark has used nationwide data to explore infertility.

It found long-term exposure to air pollution and traffic noise may be associated with higher infertility — but these factors affect men and women differently.

What do pollution and noise do to the body?

We know traffic pollution has undeniable impacts on the environment. Its negative effects on human health are also well established, with links to cancers and heart disease.

Inhaled chemicals from polluted air may also travel to the reproductive tract via the blood. They can reduce fertility by either disrupting hormones or causing direct damage to eggs and sperm.

Effects of traffic noise on health are less clear, but some research suggests this affects stress hormones, which could alter fertility.

Related: Chemicals in plastics and cosmetics tied to preterm birth risk

What did they look at?

This new study was conducted in Denmark, which collects data about every resident into multiple national databases over their lifetime, using a unique identification number.

Nationwide data allows researchers to investigate links between a person's health and factors such as where they live, their job, education history and family. This method is called "data linkage".

The study aimed to capture people who were likely to be trying to get pregnant, and therefore at risk of receiving an infertility diagnosis.

Over 2 million men and women were identified as being of reproductive age. The study looked at those who were:

• aged 30 - 45
• living together or married
• with less than two children
• living in Denmark between January 1 2000 and December 31 2017.

It excluded anyone who was diagnosed with infertility before age 30, lived alone or in a registered same-sex partnership. People with incomplete information (like a missing address) were also excluded.

There were 377,850 women and 526,056 men who fit these criteria.

The study did not survey them. Instead, over a five-year period it cross-checked detailed information about where they lived and whether they received an infertility diagnosis, collected from the Danish National Patient Register.

Researchers also estimated how much each residential address was exposed to road traffic noise (measured in decibels) and air pollution, or how much fine particulate matter (called PM2.5) is in the air.

What did they find?

Infertility was diagnosed in 16,172 men (out of 526,056) and 22,672 women (out of 377,850).

The study found the risk of infertility was 24% greater for men exposed to PM2.5 levels 1.6 times higher than recommended by the World Health Organization.

For women, exposure to traffic noise at 10.2 decibels higher than average (55-60 decibels) was associated with 14% increased infertility risk for those over 35.

Risks were similar based on residing in urban or rural areas, and when accounting for education and income.

What does it suggest?

The study highlights how environmental exposure can have immediate and long-term effects, and may affect male and female reproduction differently.

After puberty, men constantly produce sperm — up to 300 million a day. The impact of environmental changes on male fertility — such as exposure to toxic pollutants — tends to show up more quickly than in females, affecting sperm number and quality.

In contrast, women are born with all their eggs, and cannot produce new ones. Eggs have some "damage control" mechanisms to protect them from environmental hazards across a lifetime.

This doesn't mean eggs are not sensitive to damage. However it may take longer than the five years of exposure this study looked at for the impact on women to become clear.

It is possible even longer-term studies could reveal a similar impact for pollution on women.

Is data linkage a good way to look at fertility?

Data linkage can be a powerful tool to uncover links between environmental exposures and health. This allows assessments in large numbers of people, over long periods of time, like this recent Danish study.

But there are inherent limitations to these types of studies. Without surveying individuals or looking at biological factors — like hormone levels and body mass — the research relies on some assumptions.

For example, this study involved some major assumptions about whether or not couples were actually trying to conceive.

It also calculated people's exposure to noise and air pollution according to their address, assuming they were at home.

A more precise picture could be painted if information was gathered from individuals about their exposure and experiences, including with fertility.

For example, surveys could include factors like sleep disturbance and stress, which can alter hormone responses and impact fertility. Exposure to chemicals that disrupt hormones are also found at home, in everyday household and personal care products.

In its scale, this study is unprecedented and a useful step in exploring the potential link between air pollution, traffic noise and infertility. However more controlled studies — involving actual measures of exposure instead of estimations — would be needed to deepen our understanding of how these factors affect men and women.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

The shipping industry's attempt to reduce air pollution has inadvertently accelerated global warming in the short term and contributed to record-breaking sea temperatures, according to a new climate model.

Recent global shipping regulations slashed the sulfur dioxide emissions from cargo ships by a dramatic 80%. But this rapid reduction in sulfur pollution may have "created an inadvertent geoengineering termination shock with global impact," a new study has suggested. 

"The warming effect is consistent with the recent[ly] observed strong warming in 2023 and [is] expected to make the 2020s anomalously warm," the researchers wrote. The warming is equivalent in magnitude to "80% of the measured increase in planetary heat uptake since 2020."

And this reduction in pollution "could lead to a doubling (or more) of the warming rate in the 2020s compared with the rate since 1980," the researchers suggested in the new study, published May 30 in the journal Communications Earth and Environment.

Related: The 165-year reign of oil is coming to an end. But will we ever be able to live without it?

The new shipping regulations, which were implemented in 2020 by the International Maritime Organization (IMO) reduced the maximum sulfur content in shipping fuel from 3.5% to 0.5%, with the aim of improving air quality and preventing an estimated 30,000 premature deaths each year. 

But aerosols such as sulfur dioxide particles are highly reflective, and when they are released they settle in the stratosphere and bounce the sun's rays back into space — sometimes acting as a giant planetary sunblock. 

So when the regulations brought decades of massive pollution to an end, they began an unintended geoengineering experiment. Since March 2023, the loss of the sulfurous fog — combined with accelerating global warming due to burning fossil fuels, the El Niño climate pattern and the 2022 eruption of the Hunga Tonga-Hunga Ha'apai volcano — has sent average sea surface temperatures to record-shattering highs.

However, other climate scientists have disputed some of the study's conclusions. Gavin Schmidt, the director of NASA's Goddard Institute for Space Studies, told Live Science that, while the researchers' estimate for the increased solar energy entering Earth's atmosphere is accurate, "their estimate of the temperature response is not quite right, I think."

Schmidt pointed to an analysis made by Zeke Hausfather, a climate scientist at the Breakthrough Institute, which argues that the study's warming calculation relies on an overly simplified model that misunderstands heat uptake from the ocean, meaning the study overstates the sulfur reduction's warming impact. 

"We are still waiting on updated analyses related to the HTHH [Hunga Tonga-Hunga Ha'apai] volcano, other aerosol emissions, the solar cycle and various aspects of internal variability," Schmidt added. "That is on top of other analyses of the IMO rules that are ongoing."

The findings come at a time when governments are eyeing up controversial solar radiation management (SRM) techniques, which propose to dim the sunlight reaching Earth by intentionally releasing aerosols such as sulfur dioxide into the atmosphere. 

But Schmidt believes that these techniques are not viable. 

"I strongly doubt that this [solar radiation management] will ever be part of any sustainable response to climate change — but the issues that underlie that conclusion have very little to do with the science and almost everything to do with how such an effort is governed and how fragile it will be to economic or geopolitical uncertainties," Schmidt said. 

Scientists are tracking a massive plume of toxic gas moving across northern Europe that was spat out by the ongoing volcanic eruption in Iceland. The gas cloud is unlikely to cause any serious health problems. However, it could impact the ozone hole above the Arctic, experts warn.

On March 16, an underground volcano in Icealnd's Reykjanes Peninsula blew its top for the fourth time in as many months, opening up the largest fissure of the current eruption cycle and unleashing a massive lava flow that narrowly missed the evacuated town of Grindavík. There were initially fears that the lava flow could reach the sea and unleash a plume of hydrochloric acid, which would have been "life-threatening" to anyone close to the coastline, Live Science previously reported. However, the lava never reached the shore. 

But the eruption did release sulfur dioxide — a colorless, toxic gas that can be extremely dangerous in high concentrations.  

On March 17, the volcano was spitting out around 110 pounds (50 kilograms) of sulfur dioxide every second, according to a translated statement from the Icelandic Met Office. Workers at the nearby Svartsengi power plant were evacuated from the facility due to high levels of the gas, Icelandic news site RÚV reported, and locals were temporarily warned to stay inside, according to Iceland's Civil Protection.   

Sulfur dioxide emissions have diminished significantly since March 18, but new data from the Copernicus Atmosphere Monitoring Service (CAMS) — part of the European Union's Copernicus program, which tracks weather and climate changes using satellite data — shows that the initial outpouring of gas formed a 3-mile-tall (5 kilometers) concentrated column that has since blown toward other countries in northern Europe.

Related: Heat bursts from Iceland's recent eruptions in eerie NASA satellite image

The gas plume has already passed above the U.K. and is currently approaching Scandinavia, where it will begin to dissipate before entering Russia.

CAMS will continue to track the plume "although we don't expect there to be any impact on surface air quality or climate," senior CAMS scientist Mark Parrington said in a statement emailed to Live Science.

However, tracking sulfur dioxide emissions is still important because the gas can react with atmospheric ozone molecules, depleting the amount of this protective substance in the ozone layer, which shields Earth's surface from the sun's harmful ultraviolet rays. 

In October 2023, scientists partially attributed the near-record-largest ozone hole above Antarctica to the 2022 eruption of an underwater volcano in Tonga, which released high levels of water vapor into the atmosphere that may have depleted ozone levels.

Experts predict that the recent eruptions in Iceland could be the beginning of a new centuries-long period of activity in the region. As a result, the amount of sulfur dioxide being pumped toward the Arctic could also rise over the next few years, which could lead to larger northern ozone holes in the future.

"The impacts of the volcanic eruptions in Iceland in the atmosphere have not yet been so severe, but it is relevant to keep monitoring the evolution of the situation," CAMS director Laurence Rouil said in the statement.

People in the U.K. have volunteered to inhale diesel exhaust, cleaning products and cooking fumes to help unravel the effects of air pollution on the brain.

The study is being conducted by researchers affiliated with the University of Manchester and the University of Birmingham, as well as by health care providers from Manchester University National Health Service (NHS) Trust. The research team specifically recruited volunteers who were more than 50 years old and had a family history of Alzheimer's disease or another type of dementia.

There's a well-established link between exposure to air pollution and the risk of dementia, with regions with high concentrations of pollution seeing higher rates of dementia than less-impacted areas. However, scientists don't completely understand how the pollution might be driving changes in the brain.

"What we're trying to do in this study is to actually do experiments to understand why there's an association, to find out what the underlying biological mechanisms are that link air pollution to adverse effects on the human brain," Dr. Ian Mudway, an environmental toxicologist at Imperial College London, told BBC News.

Related: Could vaccines prevent and treat Alzheimer's disease?

According to a brief description of the trial, posted Dec. 14 to the preprint database medRxiv, the study participants will be exposed to four pollutants: wood smoke, diesel exhaust, cleaning products and cooking emissions. Clean air serves as a point of comparison. At present, there are 13 study participants, BBC News reported.

Each volunteer will be exposed to the pollutants one at a time, at separate sessions conducted over several months; the study protocol didn't specify the exact concentrations of the pollutants. During each exposure session, the volunteer will be exposed to either a pollutant or fresh air for one hour via a fitted mask with a tube that allows the substance to flow in. 

Neither the volunteers nor the researchers collecting data will know which pollutant a volunteer will be exposed to at a given session, to avoid bias. Before and after each exposure, the participants will complete a breathing test called a spirometry, have their blood drawn for testing and complete various cognitive tests. Volunteers are compensated for each session they attend, and they're monitored for signs of any side effects during the experiment, especially respiratory symptoms like shortness of breath.

The goals of the study are to identify some of the most hazardous components of outdoor and indoor air pollutants and to determine how they might drive degenerative processes in the brain. 

It's possible, for example, that the pollutants act on the brain directly, reaching brain cells via nerves in the nose or through the bloodstream. Alternatively, the pollutants might injure the brain indirectly by triggering widespread inflammation in the body that can then have secondary effects on the brain, the researchers wrote in their medRxiv report.

"At the moment we just don't know," Gordon McFiggans, a project lead and professor of atmospheric science at the University of Manchester, told BBC News. Although fairly small, the study is still one of the largest ever aimed at addressing this question experimentally in humans, rather than in animals, the BBC reported. Time will tell what its results reveal.

This article is for informational purposes only and is not meant to offer medical advice.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

For a day or two during wildfire season, cities like New York, Chicago, San Francisco, Sacramento and Seattle earn the dubious title of worst air quality in the world, according to real-time data from air sensor company IQAir.

But most of these cities don't typically have such polluted air. So which cities regularly have the worst air quality, and why?

Air pollution is often measured in terms of the concentration of particulate matter (PM), or a mix of solid and liquid droplets suspended in the air. Hundreds of cities have air year-round that the U.S. EPA considers unhealthy for just one day, according to the World Health Organization's (WHO) most recent data on PM2.5 small particle pollution, or those inhalable particles smaller than 2.5 micrograms.

An IQAir report found that Lahore, Pakistan had the worst air quality in 2022. Hotan in China ranked number two, followed by a suburb of Delhi, India. In 2021 the top three most polluted cities were in India; among the world’s capital cities, Delhi ranked first, then Dhaka, Bangladesh and N'Djamena, Chad. These cities all averaged more than 90 micrograms per meter cubed of PM2.5 over the course of the year, or nearly 20 times the recommended level.

Related: Even brief exposure to diesel exhaust alters activity in key brain network, study finds

Despite these rankings revealing some air pollution hotspots, it's impossible to determine which cities really have the worst air. The sensors used vary in quality, while many countries in Africa don't appear on the list because they don't report any data at all. The WHO uses only high-quality sensors, but it does not even try to rank cities: A spokesperson told Live Science that collection procedures vary too widely.

Even the metric being measured, PM2.5, has limitations. Inhaling small particles can cause health problems, and very few cities meet the WHO's most stringent PM2.5 guideline. But the chemical composition of these particles may also impact health. A WHO spokesperson said that research is not conclusive, but it is possible that cities with the same PM2.5 levels overall might have different health outcomes depending on the source of pollution.

There are several reasons why some cities have more PM2.5 than others. One is geography. Hotan is near the Taklamakan desert and experiences frequent dust storms. N'Djamena, likewise, is near the southern edge of the Sahara Desert. Mountains can impact air quality by making it harder for pollutants to disperse: Delhi, Lahore, Dhaka, and many other cities with unhealthy air lie just south of the Himalayas.

In Delhi, for instance, "just touch anything and you will have the dust, even if you clean every day," said Umesh Kulshrestha, the former dean of the School of Environmental Sciences at Jawaharlal Nehru University in New Delhi. Infrequent rain outside of the monsoon season helps dust accumulate — not only from far-off deserts, but also from unpaved roads and construction work in Delhi itself.

In addition, Delhi’s PM2.5 pollution also comes from fossil fuels. Fossil fuels harm air quality in cities worldwide. Indirectly, they increase global temperatures, which means more wildfires burn and more green spaces become deserts. Both those processes add PM2.5 to the air. Emissions from vehicles, power plants, and industrial sources also directly pollute cities locally. In a review in the journal Aerosol and Air Quality Research, Kulshrestha found that during the pandemic lockdowns in early 2020, Delhi's air quality improved, with its index score going down by 41%, thanks to reduced vehicle and industrial emissions.

Kulshrestha told Live Science that in South Asia, other common PM2.5 sources include brick kilns, crop burning, and the biofuels that many households still rely on for cooking and heating. He said that India is working to increase renewable energy sources and to replace biofuels with liquid natural gas — while this contributes to global warming, it can lower household PM2.5.

The U.S. remains the world's second-largest consumer of fossil fuels after China, contributing to poor air quality worldwide. Decades ago, though, persistent smog trapped in California's Los Angeles Basin prompted the Clean Air Act, which has since improved air pollution across the U.S.

Likewise, today's most polluted cities are also taking action to protect their skies. In Dhaka, bans on inefficient, highly-polluting two-stroke engines in three-wheeled vehicles helped keep PM2.5 levels from vehicle emissions steady as the city grew. Even though many Chinese cities are among the most polluted, there has been a dramatic decrease in pollution over the past decade since the country implemented clean air policies. In Delhi, Kulshrestha is pushing to create artificial lakes. More water should mean more evaporation, more rain and — Kulshrestha's research predicts — at least a little less dust.

Editor's Note: This story was updated on Sept. 8, 2023 to note that Umesh Kulshrestha is former, not current dean of the School of Environmental Sciences at Jawaharlal Nehru University in New Delhi.

Even brief exposures to diesel fumes may alter the brain's function, messing with how signals zip through a major brain network, a new study suggests.

Past studies suggest that people exposed to air pollution may be more likely to develop mental health conditions and neurodegenerative diseases. Now, the new study, published Jan. 14 in the journal Environmental Health, shows that exposure to diluted diesel exhaust resulted in less "functional connectivity" in a key brain network than exposure to filtered air. 

Functional connectivity is a measure of how well different brain regions communicate with one another; after exercising in clean air, the study's participants showed a temporary boost in connectivity in a specific brain network, but after exposure to diesel-tainted air, the network's connectivity remained stagnant. Although the study didn't examine the cognitive impacts of the exposure, the network is linked to internal thought and introspection, and disruptions in its activity have been linked to various mental health, cognitive and attention-related disorders. 

According to its authors, the study is the first to examine the brain's response to air pollution in such a controlled way. The researchers "have made a significant contribution to what we know about the impact of exposures to pollution," said Hao Yang Tan, a lead investigator at the Lieber Institute for Brain Development in Baltimore, who was not involved in the study.

Related: 10 things you didn't know about the brain 

The researchers took snapshots of brain activity in 25 adults using functional magnetic resonance imaging (fMRI); fMRI works by detecting increased blood flow to active neurons, therefore giving an indirect indication of brain activity. Then, participants were exposed to either filtered air or air mixed with diesel exhaust for two hours while they rode an exercise bike at a relaxed pace. 

Immediately after the exposure, researchers took another fMRI. All participants took part in both the exposure and control scenarios at different times, and neither the participants nor the data collectors ever knew which group anyone was in.

The researchers examined how exposure to diesel impacts the default mode network (DMN), which is involved in self-reflection and a person's internal thoughts, rather than external stimuli, said Dr. Michael Lipton, a professor of radiology at Albert Einstein College of Medicine and medical director of MRI services at Montefiore Medical Center, who was not involved in the study. Research suggests that people with psychiatric disorders, including anxiety and depression, show distinct changes in the DMN, said Tan. 

DMN connectivity briefly increased after exposure to filtered air, which the researchers attributed to the exercise the participants were doing. Previous research has associated light exercise with increased DMN connectivity. DMN connectivity didn't change after diesel exposure. 

The new study was limited by its small size and the fact that people are exposed to higher concentrations of air pollution for longer in the real world. The study also can't show exactly how the diesel may have caused the observed changes in connectivity.

"Diesel exhaust is known to cause systemic inflammation, which could affect the brain and change the DMN," senior study author Dr. Chris Carlsten, professor and head of respiratory medicine at the University of British Columbia, told Live Science in an email. "However, this is speculative." Lipton said he's not sure such a short exposure could cause substantial inflammation in the brain. 

Tan said the study is a good first step towards better understanding how air pollution hurts the brain. It's also important to recognize that, regardless of the biological mechanisms behind this effect, there are other reasons air pollution doesn't impact everyone equally, he added. For example, socioeconomically disadvantaged communities are more likely to be exposed to air pollution, as they're more likely to live and work in polluted areas, Tan said.

Impressionist artists like Claude Monet and Joseph Mallord William (J. M. W.) Turner are famous for their hazy, dreamlike paintings. However, a new study finds that what these European painters were really depicting in their works wasn't a figment of their imagination, but an environmental disaster: air pollution.

Scientists examined approximately 100 artworks by the two impressionist painters, who dominated the art scene between the mid-18th and early 20th centuries, during the Industrial Revolution. The team discovered that what some art enthusiasts had long believed was Monet and Turner's style of painting was actually them "capturing changes in the optical environment" that were associated with a decrease in air quality as coal-burning factories began dotting European cities and spewing pollutants into the air, according to the study, published Jan. 31 in the journal Proceedings of the National Academy of Sciences.

"It is often said that Turner was born in the age of sail and died in the age of steam and coal — his lifetime spans a time of unprecedented environmental change," first author Anna Lea Albright, an atmospheric scientist with the Laboratory of Dynamic Meteorology in France, told Live Science in an email. "During the first Industrial Revolution, these large increases in air pollution were concentrated in London, which was known as the 'Big Smoke' [where Turner was based]. Monet painted later, in the second Industrial Revolution in London and Paris."

Related: Hidden Van Gogh self-portrait discovered under 'peasant woman' painting

For the study, the scientists focused on local sulfur dioxide emission levels in London and Paris during this time period and the ways air pollution can interact with light, such as by reducing the contrast of objects viewed against a background and by increasing the intensity or "whiteness" of an image, according to the study. 

They also determined that the artists' vision wasn't the cause of this trend toward hazier artworks. "Monet was not myopic; Turner did not have cataracts," a different group of researchers wrote in a 2016 study published in the journal Eye. 

"Over Turner and Monet's careers, I noticed that the contours of their paintings became hazier, the palette appeared whiter and the style transformed from more figurative to more impressionistic," Albright said. "We knew Turner and Monet were painting during the Industrial Revolution with its unprecedented environmental changes. Their stylistic transformations accord with physical expectations of how air pollution influences light."

Impressionist air pollution

Air pollution is caused when there's an increase in toxic microscopic particles in the atmosphere. The scientists likened air pollution in Paris and London during the Industrial Revolution to levels seen in modern megacities such as Beijing, New Delhi and Mexico City.

"Air pollution absorbs and scatters light, making objects at a distance look hazier," Albright explained. "By scattering background light of all wavelengths into the line of vision, the presence of air pollution gives images a whiter tint."

Those hazy, polluted scenes were then translated into some of Monet's and Turner's most renowned paintings, including Monet's "The Houses of Parliament, Sunset" (1903) and Turner's "Rain, Steam, and Speed - The Great Western Railway" (1844).

"Impressionism is often contrasted with realism, but our results highlight that Turner and Monet's impressionistic works also capture a certain reality," study co-author Peter Huybers, a professor of Earth and planetary sciences at Harvard University, told Live Science in an email. "Specifically, Turner and Monet seem to have realistically shown how sunlight filters through pollution and clouds.

"The idea that Impressionism contains certain elements of polluted realism highlights how connected we are to our environment," he added. "Our surroundings influence what we see, how we feel [and] what we focus on. Maybe a modern Turner or Monet would help us see other novel phenomena in our environment, like climate change."

Beijing has been enveloped in one of its most severe sandstorms in over a decade, which has combined with air pollution to create a toxic, gritty haze that turned skies orange and made the skyline disappear. 

The sandstorm hit the Chinese capital on Monday morning (March 15) after gale-force winds from Mongolia blew dust from the Gobi desert over the border. In Mongolia, 341 people are missing after the same sandstorm blew across the country, according to The Guardian.

Worsening the situation, Beijing's air pollution has been rising in recent weeks as the country comes out of lockdown. The Air Quality Index (AQI) for the city maxed out at a "hazardous" 999, according to the World Air Quality Index project. For context, at the same time, the AQI for New York was 26. 

Related: 7 crazy facts about dust storms

"This is the most intense sandstorm weather our country has seen in 10 years, as well as it covering the broadest area," China's National Meteorological Center said after issuing a weather alert, according to a statement.

More than 400 flights in and out of Beijing were canceled, and authorities ordered residents to stay inside, although many ventured out to capture stunning images of the city as it was engulfed in thick orange dust.

Sandstorm intensity 

 Sandstorms are not uncommon in Beijing and northern China due to their close proximity to the Gobi desert. 

During the 1950s, deforestation and soil erosion, especially in the north, fueled more frequent and more intense sandstorms. People cut down the forests that once stood on the border with Mongolia and provided a natural buffer against sand. However, a mass tree-planting project initiated in the 1970s has helped counteract that damage. As part of the Three-North Shelter Forest Program 87 million acres (5 million hectares) of trees will be planted near the border with Mongolia by 2050, according to Bloomberg.

As a result, the number of days in which sand has blown into Beijing annually has fallen from 26 days in the 1950s to just three days in 2010, according to Bloomberg, making sandstorms like this one an outlier. However, climate change has made winds stronger, which could worsen sandstorms in the future.

Health problems  

Beijing and other Chinese cities face horrifying levels of air pollution due to their reliance on coal power, rising population and increased car traffic. 

Air pollution is already hazardous to health, but combined with sandstorms it can become an even more serious problem, according to bloomberg.

During the current sandstorm, the levels of particulate matter 10 micrometers or less in size — called PM10 — in Beijing reached 8,000 micrograms per cubic meter, more than 160 times the safe limit set out by the World Health Organisation (WHO), according to Sky News.

If man-made air pollution continues to rise in the coming decades, sandstorms could become much more problematic for the residents of large chinese cities like Beijing, even if the sandstorms themselves become less frequent.

Originally published on Live Science.

As the world scrambles to confront the disease caused by a novel coronavirus, Italy has been forced to take such dramatic measures that the country's emissions have changed, as seen from space.

That's on display in a new video produced by the European Space Agency (ESA) using data gathered by the agency's Copernicus Sentinel-5P satellite. That spacecraft tracks air pollution in the atmosphere, and the satellite has seen a sharp decrease in emissions of nitrogen dioxide over Italy during the first two and a half months of 2020. The Italian prime minister ordered northern Italy into a lockdown on Sunday (March 8) to try to contain the disease, known as COVID-19.

"Although there could be slight variations in the data due to cloud cover and changing weather, we are very confident that the reduction in emissions that we can see coincides with the lockdown in Italy causing less traffic and industrial activities," Claus Zehner, the mission's manager at ESA, said in a statement.

Related: How would NASA handle an astronaut disease outbreak?
More: Satellite images show Iran's mass graves for coronavirus victims 

Italy has seen the greatest number of confirmed cases of COVID-19 of any country except China, where the outbreak, which is now classified as a pandemic, began. Cases were particularly prevalent in northern Italy, hence the prime minister's regulations closing public spaces there. Since then, he has extended the measures throughout the country.

As people stayed home more and more, nitrogen dioxide emissions in Italy, particularly the country's northern region, fell. Copernicus Sentinel-5P measures levels of this compound, along with ozone, sulfur dioxide, carbon monoxide and methane, among other substances. All of these gases can affect human health and the climate, which is why the ESA monitors them.

But right now, the spread of COVID-19 is a much more pressing concern, and the reduction in emissions suggests that people are taking steps to reduce their own exposure and that of their neighbors.

•  Dramatic effect of coronavirus lockdowns seen from space 
•  NASA center in California issues mandatory work-from-home order after employee tests positive for coronavirus 
•  Space Symposium 2020 postponed indefinitely due to coronavirus pandemic 

Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook. 

Black soot spewn from cars and burning fossil fuels can find its way into the womb where a fetus is developing, according to a new study.

The researchers found that the amount of soot, also called black carbon, embedded in the fetus side of the placenta correlates to the estimated air pollution found near the expectant mother's home, they described online Sept. 17 in the journal Nature Communications. 

"This is the most vulnerable period of life. All the organ systems are in development. For the protection of future generations, we have to reduce exposure," said study co-author Tim Nawrot at Hasselt University in Belgium, in an interview with The Guardian. 

Even so, the researchers can't say whether those particles actually get into the fetus, they noted in the paper.

Toxic particles found floating in polluted air have been spotted in placentas before, and a study presented at a conference in 2018 revealed that inhaled black carbon — a component of soot — can enter the placenta through the mother's bloodstream. But previous research failed to confirm that the soot could then move from the maternal placenta, made from the mother's uterine tissue, to the part of the placenta made from tissues that form the developing child and so are accessible to the fetus. The new study supplies this evidence. 

The researchers gathered placental samples from more than 20 nonsmoking women in the Belgian town of Hasselt and exposed the tissue to ultrafast laser bursts, according to Science News. The technique excites negatively charged particles within each sample and causes different tissues to radiate colored light — red for collagen, green for placental cells and white for black carbon.

Related: 9 Uncommon Conditions That Pregnancy Could Bring

They found an average of 9,500 soot particles per cubic millimeter (about the volume of a grain of salt) in the placentas of women who lived a far distance from main roads and areas of high pollution, The Guardian reported. In comparison, women living in more polluted areas accumulated about 20,900 particles of black carbon per cubic millimeter on the fetal side of their placentas.

"There's no doubt that air pollution harms a developing baby," said Amy Kalkbrenner, an environmental epidemiologist at the University of Wisconsin-Milwaukee, who was not involved in the work, in an interview with Science News. A mother's exposure to air pollution has long been linked to heightened risk of preterm birth, low birth weight and miscarriage, but the dangers were attributed to inflammation in the mother herself, particularly in the uterus. The new study suggests "air pollution itself is getting into the developing baby," Kalkbrenner said. 

Metal contaminants, including lead, have been shown to cross the placental barrier and disrupt the development of the fetus and even lead to miscarriages and stillbirths, according to the National Institute for Occupational Safety and Health. Synthetic chemicals, including pesticides and flame retardants, can also transfer into the placenta and harm the fetus, scientists reported in 2016 in the journal Current Environmental Health Reports. 

"We should be protecting foetuses and this is another reminder that we need to get [air pollution] levels down," said Jonathan Grigg of Queen Mary University of London, whose lab conducted the 2018 black carbon study, in an interview with The Guardian. An estimated 91% of the world's population lives in regions where air pollution levels exceed the recommended World Health Organization maximums; this study highlights yet another risk of letting those levels go unchecked, he said. 

• 8 Ways That Air Pollution Can Harm Your Health 
• 5 Reasons Why Placentas are Awesome 
• Having a Baby: Stages of Pregnancy 

Originally published on Live Science.

Strange Connections

We all know the basics about trying to avoid cancer: Don't smoke, slather on the sunscreen. And you can avoid a few other risk factors for cancer by doing things like skipping the red meat, getting vaccinated against HPV and steering clear of air pollution if at all possible.

But some things that may raise people's risk of cancer get a lot less attention. The National Cancer Institute estimates that 1.7 million people in the U.S. will be diagnosed with cancer in 2018 and that about 38 percent of people in the U.S. will get cancer during their lifetimes. Here's a look at seven strange things that may raise your risk of cancer — plus one thing you probably don't need to worry about.

Hot tea

Sipping tea may sound like a healthy way to cope with stress, and drinking green tea may even reduce cancer risk. But make sure to let your cup cool down first. Drinking tea that is extremely hot may increase the risk of cancer of the esophagus, according to a 2018 study done in China.

The study included about 450,000 people, and the researchers found that the people who said they usually drank tea that was "burning hot" and also smoked tobacco and drank alcohol excessively had a five times greater risk of esophageal cancer than people who did none of those three things. The extreme heat of the tea could damage the lining of the esophagus, increasing the damage done by smoke and alcohol, the researchers said.

Sitting still

One way to reduce the risk of cancer is to get moving. Higher levels of physical activity are linked with a reduced risk of some of the most common cancers, including lung, colon and breast cancers. One study found that exercise lowers the risk of getting any type of cancer by 7 percent. It's not clear exactly how exercise lowers people's risk of cancer, the researchers noted.

Yet it seems that many people are unaware of the link between exercise and reduced risk of cancer: A 2018 study found that only 3 percent of U.S. adults surveyed listed that risk reduction as one of the benefits of exercise. Increasing public awareness of the link could be a goal of public health efforts to reduce cancer rates, the researchers said.

Being tall

Taller people are more likely to get cancer than shorter people. A 2018 study found that for every extra 10 centimeters (4 inches) of height, a person's risk of cancer increases by 10 percent. Scientists discovered the link between height and cancer in the 1950s, the researchers said, and although it's not clear exactly how being taller may influence a person's cancer risk, it could be the simple fact that taller people have more cells in their bodies and therefore more cells that could become cancerous, the researchers said.

An earlier study found a 13 percent increase in postmenopausal women's risk of cancer with every extra 4 inches of height. And, interestingly, a 2016 study found a link between longer legs and people's risk of colon cancer. It could be that the level of growth factors in the body play a role in the link, the researchers of the colon cancer study said.

Smoke from the grill

Summer cookouts aren't as innocent as they may look. People who sit close to a grill may absorb an increased amount of chemicals called polycyclic aromatic hydrocarbons (PAHs) through their skin, a 2018 study found. Those chemicals are released by the burning of wood or charcoal and are known to be carcinogens, or cancer-causing agents.

The researchers noted that the level of PAHs that people absorbed through their skin was less than the level they were exposed to by eating the grilled meat. But still, people picked up higher levels of PAHs through their skin than they did by breathing in the smoke. It may help a bit to cover up when grilling, the researchers concluded. People's clothing may lower the level of PAHs that are absorbed through the skin over the short term.

Breast implants

Women with a certain type of breast implant may face an increased risk of a rare type of lymphoma called anaplastic large cell lymphoma (ALCL), a 2018 study found. This type of cancer is not a breast cancer; lymphomas are cancers that arise from the cells of the immune system. Among the women in the study, those who had breast implants that were textured, rather than smooth-surfaced, were at a higher risk of ALCL, the researchers said.

Still, the general risk of this cancer even among women with implants is very low. The researchers calculated that for every 7,000 women who get breast implants, 1 will go on to develop ALCL in the breast by the time she is 75. Although the reason for the link is not exactly clear, it is possible that the implants trigger increased inflammation in the breast tissue, which could lead to cancer over time, the researchers said.

Alcohol

Raising a glass and toasting to good health may not be a great idea. Researchers estimate that 5 percent of annual new cancer cases worldwide and 6 percent of yearly cancer deaths are directly due to drinking alcohol, according to a 2018 statement from the cancer doctors' group, the American Society of Clinical Oncology. Alcohol is linked to increased risks of breast, colorectal, esophageal and liver cancers, as well as cancers of the mouth and throat. And although heavier drinking is generally linked with a higher cancer risk, research shows that drinking even light or moderate amounts of alcohol may increase people's risk of cancer.

Researchers recently found evidence supporting one idea for how alcohol contributes to cancer risk. A 2018 study in mice found that the breakdown of alcohol in the body may release a chemical that damages the DNA of the stem cells of the blood, which could lead to cancer.

Too much weight

Having a higher body weight may increase the risk of more than a dozen types of cancer, a 2017 study found. People in the study who were overweight or obese faced nearly double the risk of cancers of the esophagus, stomach, liver and kidney compared with people who were in the normal weight range.

People who are overweight or obese may harbor higher levels levels of inflammation, thus increasing their cancer risk, the report said. Or, higher levels of hormones that are linked to cell growth may be behind the increased risk, the researchers said.

A 2017 study found that people who maintained a healthy lifestyle, including a lower body weight, had a lower risk of cancer than those with a less healthy lifestyle.

1 thing that probably doesn't cause cancer

Still, if it seems that everywhere you turn, you find something that may cause cancer, take comfort in this: Research suggests there's no link between the electromagnetic signals from cellphones and people's risk of cancer.

In a 10-year study published in 2018, researchers looked at the effects of very high levels of radio-frequency radiation on cancer rates in lab rats. They concluded that there is no evidence that the levels of radio-frequency radiation that people are exposed to when they use cellphones are harmful to human health.

The harmful effects of air pollution affect far more than a person's respiratory system; previous research has found that it can also hurt babies in the womb.

Now, a new, small study offers insights into precisely how air pollution can harm fetuses. In the study, researchers found microscopic soot particles in the placentas of pregnant women living in London, suggesting that these harmful particles can pass into the umbilical cord.

Earlier studies have shown that there's an "association between maternal exposure to air pollution and effects on the fetus,” said study co-author Lisa Miyashita, a postdoctoral researcher at Queen Mary University of London (QMUL). Miyashita's new research was presented at the European Respiratory Society International Congress in Paris on Sept. 16. The findings have not yet been published in a peer-reviewed journal. [7 Ways Pregnant Women Affect Babies]

The previous studies found that problems including "premature birth, low birth weight, infant mortality and childhood respiratory problems seem to be linked to the mothers' exposure to air pollution," Miyashita told Live Science. No studies, however, have looked at the potential mechanisms behind this association, she added.

To explore the link, Miyashita and her colleagues looked at immune cells called macrophages taken from the placentas of five women, all of whom delivered healthy babies via cesarean section. None of the women's pregnancies had complications, and none of the women were smokers.

Macrophages are white blood cells that can be found in all types of tissues in the body. They're tasked with hunting down threats to the body such as germs, cancer cells and air pollution particles. Once they detect a threat, they engulf it and digest it, to prevent it from harming the body.

The QMUL team has previously studied macrophages taken from the lungs of Londoners and found that they were full of air pollution particles, Miyashita said. The researchers wanted to see if they could also find these particles in macrophages taken from the placenta, a finding that would mean the air pollution particles had crossed into the bloodstream from the lungs.

Indeed, a few recent studies have hinted that so-called ultrafine particles — particles smaller than 100 nanometers in diameter — might be able to do just that, Miyashita said.

Still, the researchers had no idea whether they'd find anything at all, she added.

Placenta cells under the microscope

Using powerful microscopes, the team looked at 3,500 placental macrophages taken from the five women. In 60 of those cells, the scientists found black areas that looked "exactly the same" as the pollution-filled macrophages taken from lung cells, Miyashita said. Contaminated cells were found in samples from all five placentas in the study.

The researchers only found the polluted macrophages in the placental cells; they didn't look for pollution-filled cells in the umbilical cord, which connects the placenta to the fetus, or in the fetus itself. But even if the particles remain in the placenta and don't cross over into the fetus, they could still negatively affect the baby's health, lead study author Dr. Norrice Liu, a pediatrician at QMUL, said in a statement.

"We do not know whether the particles could move across into the fetus," Liu said. “Our evidence suggests that this is indeed possible, but even if they only have an effect on the placenta, this will have a direct impact on the fetus."

That's because “these are fine particles, [and] all fine particles stimulate inflammatory processes" that could harm the fetus, said Dr. Tobias Welte, the vice president of the European Respiratory Society and a professor of pulmonary medicine at the University of Hannover, Germany, who was not part of the study. “Some of these particles could be more toxic and carcinogenic than others, but they are all bad for the body."

Welte said that the new results are significant, because they show for the first time that ultrafine air- pollution particles can directly affect unborn children.

The understanding of air pollution, he said, is shifting, as more studies show that ultrafine air pollution particles don't just stay in the lungs but penetrate further into the body where they could cause harm. [8 Ways That Air Pollution Can Harm Your Health]

"Air pollution is no longer a respiratory problem, it's a systemic problem," Welte told Live Science. "Our hearts, brains, kidneys and lymph nodes could be virtually full of these particles. The exposure of unborn children to these particles is particularly worrying as it can affect the development of their organs."

Miyashita said that pregnant woman living in cities with high levels of air pollution should try to avoid busy roads and areas as much as possible to reduce their exposure.

The researchers are planning to conduct a larger study to develop a better understanding of how the presence of these particles in the placenta might affect the health and development of children.

Originally published on Live Science.

Pollution is the process of making land, water, air or other parts of the environment dirty and not safe or suitable to use. This can be done through the introduction of a contaminant into a natural environment, but the contaminant doesn't need to be tangible. Things as simple as light, sound and temperature can be considered pollutants when introduced artificially into an environment. 

Toxic pollution affects more than 200 million people worldwide, according to Pure Earth, a non-profit environmental organization. In some of the world's worst polluted places, babies are born with birth defects, children have lost 30 to 40 IQ points, and life expectancy may be as low as 45 years because of cancers and other diseases. Read on to find out more about specific types of pollution.

Land pollution

Land can become polluted by household garbage and by industrial waste. In 2014, Americans produced about 258 million tons of solid waste, according to the U.S. Environmental Protection Agency. A little over half of the waste — 136 million tons— was gathered in landfills. Only about 34% was recycled or composted. 

Organic material was the largest component of the garbage generated, the EPA said. Paper and paperboard accounted for more than 26%; food was 15% and yard trimmings were 13%. Plastics comprised about 13% of the solid waste, while rubber, leather and textiles made up 9.5% and metals 9%. Wood contributed to 6.2% of the garbage; glass was 4.4% and other miscellaneous materials made up about 3%.

Commercial or industrial waste is a significant portion of solid waste. According to the University of Utah, industries use 4 million pounds of materials in order to provide the average American family with needed products for one year. Much of it is classified as non-hazardous, such as construction material (wood, concrete, bricks, glass, etc.) and medical waste (bandages, surgical gloves, surgical instruments, discarded needles, etc.). Hazardous waste is any liquid, solid or sludge waste that contain properties that are dangerous of potentially harmful to human health or the environment. Industries generate hazardous waste from mining, petroleum refining, pesticide manufacturing and other chemical production. Households generate hazardous waste as well, including paints and solvents, motor oil, fluorescent lights, aerosol cans and ammunition.

Water pollution

Water pollution happens when chemicals or dangerous foreign substances are introduced to water, including toxic chemicals, sewage, pesticides and fertilizers from agricultural runoff, or metals like lead or mercury. According to the Environmental Protection Agency (EPA), 44% of assessed stream miles, 64% of lakes and 30% of bay and estuarine areas are not clean enough for fishing and swimming. The EPA also states that the United State's most common contaminants are bacteria, mercury, phosphorus and nitrogen. These come from the most common sources of contaminates, that include agricultural runoff, air deposition, water diversions and channelization of streams.

Water pollution isn't just a problem for the United States. According to United Nations, 783 million people do not have access to clean water and around 2.5 billion do not have access to adequate sanitation. Adequate sanitation helps to keep sewage and other contaminants from entering the water supply.

According to National Oceanic and Atmospheric Administration (NOAA), 80% of pollution in marine environment comes from the land through sources like runoff. Water pollution can also severely affect marine life. For example, sewage causes pathogens to grow, while organic and inorganic compounds in water can change the composition of the precious resource. According to the EPA, low levels of dissolved oxygen in the water are also considered a pollutant. Dissolved  is caused by the decomposition of organic materials, such as sewage introduced into the water.

Warming water can also be harmful. The artificial warming of water is called thermal pollution. It can happen when a factory or power plant that is using water to cool its operations ends up discharging hot water. This makes the water hold less oxygen, which can kill fish and wildlife. The sudden change of temperature in the body of water can also kill fish. According to the University of Georgia, it is estimated that around half of the water withdrawn from water systems in the United States each year is used for cooling electric power plants. 

"In nearly all cases, 90% of this water is returned to its source, where it can raise the water temperature in an area immediately surrounding the water discharge pipe. Depending on water flow, the water temperature quickly returns to ambient temperatures that do not harm fish." Donn Dears, former president of TSAugust, a not for profit corporation organization focused on energy issues, told Live Science.

Nutrient pollution, also called eutrophication, is another type of water pollution. It is when nutrients, such as nitrogen, are added into bodies of water. The nutrient works like fertilizer and makes algae grow at excessive rates, according to NOAA. The algae blocks light from other plants. The plants die and their decomposition leads to less oxygen in the water. Less oxygen in the water kills aquatic animals.

Air pollution

The air we breathe has a very exact chemical composition; 99% of it is made up of nitrogen, oxygen, water vapor and inert gases. Air pollution occurs when things that aren't normally there are added to the air. A common type of air pollution happens when human activity releases particles into the air from burning fossil fuels. This pollution looks like soot, containing millions of tiny particles, floating in the air. 

Another common type of air pollution is dangerous gases, such as sulfur dioxide, nitrogen oxides, carbon monoxide and chemical vapors. These can take part in further chemical reactions once they are in the atmosphere, creating acid rain and smog. Other sources of air pollution can come from within buildings, such as secondhand smoke. 

Finally, air pollution can take the form of greenhouse gases, such as carbon dioxide or sulfur dioxide, which are warming the planet through the greenhouse effect. The greenhouse effect is when gases absorb the infrared radiation that is released from Earth, preventing the heat from escaping. This is a natural process that keeps our atmosphere warm. If too many gases are introduced into the atmosphere, though, more heat is trapped and this can make the planet artificially warm, according to Columbia University. 

Air pollution kills more than 2 million people each year, according to a study published in the journal of Environmental Research Letters. The effects of air pollution on human health can vary widely depending on the pollutant, according to Hugh Sealy, professor and director of the environmental and occupational health track at the Department of Public Health and Preventive Medicine, St. George's University, St. George's, Grenada. If the pollutant is highly toxic, the effects on health can be widespread and severe. For example, the release of methyl isocyanate gas at Union Carbide plant in Bhopal in 1984 killed over 2,000 people, and over 200,000 suffered respiratory problems. An irritant (e.g. particulates less than 10 micrometers) may cause respiratory illnesses, cardiovascular disease and increases in asthma. "The very young, the old and those with vulnerable immune systems are most at risk from air pollution. The air pollutant may be carcinogenic (e.g. some volatile organic compounds) or biologically active (e.g. some viruses) or radioactive (e.g. radon). Other air pollutants like carbon dioxide have an indirect impact on human health through climate change," Sealy told Live Science.

Noise pollution

Even though humans can't see or smell noise pollution, it still affects the environment. Noise pollution happens when the sound coming from planes, industry or other sources reaches harmful levels. Research has shown that there are direct links between noise and health, including stress-related illnesses, high blood pressure, speech interference, hearing loss. For example, a study bythe WHO Noise Environmental Burden on Disease working group found that noise pollution may contribute to hundreds of thousands of deaths per year by increasing the rates of coronary heart disease. Under the Clean Air Act, the EPA can regulate machine and plane noise.

Underwater noise pollution coming from ships has been shown to upset whales' navigation systems and kill other species that depend on the natural underwater world. Noise also makes wild species communicate louder, which can shorten their lifespan.

Light pollution

Most people can't imagine living without the modern convenience of electric lights. For the natural world, though, lights have changed the way that days and nights work. Some consequences of light pollution are:

• Some birds sing at unnatural hours in the presence of artificial light. 
• Scientists have determined that long artificial days can affect migration schedules, as they allow for longer feeding times. 
• Streetlights can confuse newly hatched sea turtles that rely on starlight reflecting off the waves to guide them from the beach to the ocean. They often head in the wrong direction. 
• Light pollution, called sky glow, also makes it difficult for astronomers, both professional and amateur, to properly see the stars.
• Plant's flowering and developmental patterns can be entirely disrupted by artificial light.
• According to a study by the American Geophysical Union, light pollution could also be making smog worse by destroying nitrate radicals that helps the dispersion of smog.

Turning on so many lights may not be necessary. Research published by International Journal of Science and Research estimates that over-illumination wastes about 2 million barrels of oil per day and lighting is responsible for one-fourth of all energy consumption worldwide.

Other pollution facts:

• Americans generate 30 billion foam cups, 220 million tires, and 1.8 billion disposable diapers every year, according to the Green Schools Alliance.
• According to the WHO, ambient air pollution contributes to 6.7% of all deaths worldwide.
• The Mississippi River drains the lands of nearly 40% of the continental United Sates. It also carries an estimated 1.5 million metric tons of nitrogen pollution into the Gulf of Mexico each year, resulting in a dead zone each summer about the size of New Jersey.
• Pollution in China can change weather patterns in the United States. It takes just five days for the jet stream to carry heavy air pollution from China to the United States, where it stops clouds from producing rain and snow.
• About 7 million premature deaths annually linked to air pollution, according to WHO. That is one in eight deaths worldwide. 

Additional resources

• WHO: World Water Day Report
• EPA: Water Quality Facts
• Columbia University: The Greenhouse Effect and Global Warming
• U.S. National Library of Medicine: Noise Pollution
• Green School Alliance: Pollution Facts

Breathe deep

An estimated 3.3 million deaths worldwide are caused by outdoor air pollution, according to a study published in September 2015 in the journal Nature. Of those deaths, about 75 percent are from heart attacks or strokes, while about 25 percent are from lung-related ailments, Live Science previously reported.

The majority of these deaths — about 75 percent — happen in Asia, where air pollution is particularly severe, especially in China and India. Much of this pollution results from burning fossil fuels, and global carbon emissions are on track to reach record highs worldwide in 2017, according to a report released Nov. 13, 207, by the Global Carbon Project.

The link between cardiovascular health and air pollution is well-known, but recent studies are providing a growing body of evidence that polluted air can have a range of negative impacts on physical and mental health, leading to ailments that can in some cases prove lethal. 

Poor quality sperm

Elevated levels of air pollution have been linked to lower sperm quality, according to a study from Taiwan published Nov. 13 in the journal Occupational and Environmental Medicine.

Researchers investigated sperm production, activity and appearance over a series of three-month periods, in nearly 6,500 men living in Taiwan that were between the ages of 15 and 49. They then estimated how the subjects' sperm would be affected over a two-year period.

The scientists found an association between exposure to fine particulate matter in the air and abnormal sperm shape and size, they reported in the study. However, the amount of sperm produced tended to be higher when air pollution was present, perhaps to compensate for the compromised morphology of the individual sperm cells, the study authors noted. 

Fractures from bone density loss

In older people, osteoporosis — age-related bone density loss — is the most common cause of bone fractures, leading to approximately 8.9 million fractures in people around the world each year, according to the International Osteoporosis Foundation. And there may be a link between air pollution and greater vulnerability to broken bones from osteoporosis, scientists reported in a study published Nov. 9, 2017, in the journal The Lancet: Planetary Health.

Researchers first evaluated data from 9.2 million people over the age of 65, investigating hospital admissions for bone fractures in the northeast and mid-Atlantic United States from January 2003 to December 2010. They compared their findings about patients with broken bones to levels of particulate matter in the air — a component of air pollution — and found that the risk of bone fractures increased when pollution levels were higher, particularly in low-income communities.

In a second stage of analysis, the researchers looked at 692 middle-age men in the Boston area, examining the impacts of their exposure to air pollution over time. They observed that men living in regions where pollution from car emissions was higher, had lower levels of parathyroid hormone, which contributes to building and maintaining bone mass. The men in highly polluted areas also had greater drops in their bone density levels than study subjects living in less polluted neighborhoods, the scientists reported.   

Stroke risk

Strokes kill an estimated 5 million people worldwide each year — they are the fifth leading cause of death in the United States and are a major cause of long-term disability, according to the Centers for Disease Control and Prevention. And incidences of stroke are on the rise, leading a team of researchers to question whether environmental factors could be to blame.

Scientists reviewed 94 studies reporting 6.2 million stroke cases in 28 countries around the world, occurring between 1948 and 2014. They were looking for associations between short-term exposure to air pollution — evaluating pollution from gasses and from particles in the air — and hospital admission or death resulting from a stroke.

They discovered a "marked and close association" between short periods of exposure to certain levels of air pollution and "adverse stroke outcomes" — disabilities and deaths — which they described in a study published in May 2015 in the journal BMJ. Though only 20 percent of the studies represented developing countries, air pollution levels tended to be highest there, and the number of strokes reported were also disproportionately high, the scientists wrote in the study.  

Kidney disease

A recent study of U.S. veterans suggested that air pollution exposure could be connected to declining kidney function, the emergence of kidney disease and even kidney failure. In the study, which was published online on Sept. 21 , 2017, in the Journal of the American Society of Nephrology, researchers reported that even low levels of air pollution could affect the kidneys, and its impact would increase linearly as pollution levels rose.

The scientists analyzed medical data representing over 2 million U.S. veterans and spanning more than eight years. They also collected information on the air pollution levels in areas where the veterans lived, which was gathered by NASA satellites. Their findings noted that air pollution levels below the recommended levels established by the Environmental Protection Agency (EPA) could be linked to kidney deterioration, with thousands of new cases of kidney disease or failure developing each year in areas where pollution levels were higher than the recommended limit, the study authors wrote.

"Even levels below the limit set by the EPA were harmful to the kidneys," Dr. Ziyad Al-Aly, director of clinical epidemiology at the Veterans' Affairs Saint Louis Health Care System, said in a statement.

"This suggests that there is no safe level of air pollution," Al-Aly added. 

High blood pressure

A study of over 41,000 people living in Spain, Germany, Denmark, Sweden and Norway, found that air pollution could increase the risk of developing high blood pressure, or hypertension, as much as being overweight would. The study — published in October 2016 in the European Heart Journal — was part of an ongoing project known as "European Study of Cohorts for Air Pollution Effects" (ESCAPE), which is exploring how human health in Europe is affected by long-term exposure to air pollution.

None of the people who joined the study in 2008 suffered from hypertension when research began. But during follow-up visits with the scientists years later, 6,207 people — 15 percent of the study subjects — had developed hypertension or were taking medication to lower their blood pressure.

In the study, researchers discovered that in the cities' most polluted areas, one more person per 100 would be likely to develop high blood pressure, than in populations living in regions where the air was cleaner.

During three two-week periods between 2008 and 2011, scientists measured air pollution levels in 60 sites. They found the risk of hypertension in people that lived in the most polluted areas increased by 22 percent, compared to people living in areas where pollution was lowest.

"Our findings show that long-term exposure to particulate air pollution is associated with a higher incidence of self-reported hypertension and with intake of anti-hypertensive medication," study lead author Barbara Hoffman, a professor of environmental epidemiology at the Centre for Health and Society at Heinrich-Heine-University in Düsseldorf, Germany, said in a statement.

"As virtually everybody is exposed to air pollution for all of their lives, this leads to a high number of hypertension cases, posing a great burden on the individual and on society," Hoffman said.

Negative birth impacts

Recently, a study in mice found that exposure to air pollution during pregnancy could be connected to premature birth and low birth weight. These effects were found to be more likely to develop if exposure to polluted air occurred during the period of pregnancy in mice that was comparable to the first or second trimester in humans, according to research published on July 27 in the journal Environmental Health Perspectives.

In the study, the pregnant mice inhaled air containing invisible particles produced by burning fossil fuels, at levels that matched those in urban areas that are considered to be highly-polluted. The scientists discovered that exposure to polluted air during the earliest stage of pregnancy led to premature birth in 83 percent of the mice. If the mice were exposed to the pollutants from conception through the period marking the second trimester in a human mother, birth weight in 50 percent of the litters dropped by more than 11 percent.

"This first study of this problem in mice adds to the growing body of evidence that inhalation of particulate matter from implantation through the second trimester of pregnancy is potentially dangerous," study lead author Jason Blum, an assistant professor in the Department of Environmental Medicine at NYU School of Medicine, said in a statement.

Mental health issues

In addition to taking a toll on the body, air pollution can also fuel psychological distress, according to a study published in the November 2017 issue of the journal Health & Place.

For the study, researchers investigated air quality data from an air pollution database, alongside survey results from 6,000 participants from across the U.S. They assessed levels of psychological distress in participants using a scale that evaluated their descriptions of feelings of hopelessness, sadness, nervousness and other similar emotions.  

The scientists found that as the amount of pollution in the air went up, so did the risk of the people in the study reporting instances of psychological distress. Scores representing distress were 17 percent higher in areas where air pollution was higher, and trends emerged when the study authors looked at the race of participants. In regions where the air was more toxic, the level of distress reported by black men was 34 percent higher than in white men, and the difference between black men and Latino men was even more pronounced — about 55 percent higher, the scientists reported.

And white women were especially susceptible to psychological upset in the presence of more toxic air. About 39 percent of the women in the study reported greater distress in response to rising levels of pollution, according to the study.

"This is really setting out a new trajectory around the health effects of air pollution," study co-author Anjum Hajat, an assistant professor of epidemiology in the University of Washington School of Public Health, said in a statement.

"The effects of air pollution on cardiovascular health and lung diseases like asthma are well established, but this area of brain health is a newer area of research," Hajat said.

Heart attack

Inhaling polluted air can cause heart inflammation and contribute to cardiovascular disease and an increased risk of death, according to the American Heart Association. In fact, air pollution causes as many heart attacks as alcohol, coffee or exercise, according to a study published in February 2011 in the journal The Lancet.

Researchers examined 36 studies describing people who had suffered non-fatal heart attacks in different countries between 1960 and 2010. They investigated various risk factors that can contribute to heart attacks, and assessed how often people came inot contact with the different factors, to determine which triggered heart attacks more frequently, Live Science previously reported.

The scientists found that air pollution accounted between 5 and 7 percent of heart attacks, while drinking alcohol or coffee accounted for about 5 percent of heart attacks apiece, and exercise covered about 6 percent. 

From inefficient grids, shortfalls in policy, and even the occasional eclipse, solar-energy collection faces no shortage of hurdles. Scientists have discovered another stumbling block: air pollution. In certain parts of the globe, the accumulation of particulate matter on solar panels can curtail energy output by more than 25 percent, according to a new study. 

Published last week in the journal Environmental Science & Technology Letters, the study revealed that the regions most susceptible to this challenge also have the heaviest solar investments. These regions include China, India and the Arabian Peninsula.

"My colleagues in India were showing off some of their rooftop solar installations, and I was blown away by how dirty the panels were," Michael Bergin, a professor of civil and environmental engineering at Duke University and lead author of the study, said in a statement. "I thought the dirt had to affect their efficiencies, but there weren't any studies out there estimating the losses. So we put together a comprehensive model to do just that." [In Photos: The World's 10 Most Polluted Places]

Working with his counterparts at the Indian Institute of Technology-Gandhinagar, Bergin measured the efficiency of the school's photovoltaic solar panels as they thickened with grime over several months.

The chemical analysis showed that 92 percent of the muck was natural dust. The remaining 8 percent? Pollutants from human activities, such as fossil-fuel and biomass combustion.  

Although this latter group contributed a smaller percentage of the overall grime on the solar panels, it can result in greater energy loss, Bergin said.

"The man-made particles are also small and sticky, making them much more difficult to clean off," he said. In addition, smaller particles block sunlight more efficiently than natural dust does, he added.

Although scrubbing the panels produced an immediate 50 percent uptick in energy gathering, Bergin warned against it.

"The more you clean them, the higher your risk of damaging them," he said.

In certain swaths of China, where pollution has a stranglehold, human-made particles can spell losses of tens of billions of dollars every year due to solar-energy-collection dips, Bergin said. (China currently snaps up about half of the world's new solar panels.)

"We always knew these pollutants were bad for human health and climate change, but now we've shown how bad they are for solar energy as well," Bergin added. "It's yet another reason for policymakers worldwide to adopt emissions controls."

Original article on Live Science. 

Gas-powered vehicles that use cleaner technology may still be spewing tons of harmful chemicals into the atmosphere, new research suggests.

Newer "greener" vehicles are equipped with technology that traps most particulate matter and mostly emit vapors. However, those vapors may still chemically react with other compounds in the atmosphere to form pollutants — it may just take a little while longer, according to a new study. [The 10 Most Polluted Places on Earth]

Air pollution

When cars combust gasoline, they produce a mixture of vapor, teensy droplets and miniscule solid particles that leave a vehicle's exhaust pipe and rise up into the atmosphere. The solid particles, called primary organic aerosols, are what most people thnk of when they picture the sooty black particles belching from a stinky tailpipe. Some of these particles are less than about 2.5 micrometers in diameter, small enough to burrow deep into a person's lungs and even circulate in the bloodstream, according to the Environmental Protection Agency. These particles have been tied to heart and lung problems, according to a 2006 study in the Journal of Air & Waste Management Association. However, secondary organic aerosols (SOAs), which can form in a chemical reaction between sunlight and organic compounds from tailpipes, trees, and power plants, may also have an effect on health, according to the EPA.

In recent years, stricter emissions guidelines have dramatically reduced the amount of primary organic aerosols that cars can emit. But it wasn't clear how this would ultimately affect the formation of secondary compounds that could still harm health.

To find out, Allen Robinson, a mechanical engineer at Carnegie Mellon University in Pennsylvania and director of the EPA-funded Center for Air, Climate and Energy Solutions, and his colleagues put a fleet of 59 cars into a smog chamber. The cars were different ages and spanned a range of different emissions standards, from being low-emitting vehicles to super-ultra-low-emitting vehicles, which means they produce 90 percent fewer emissions than the average vehicle. The team found that newer vehicles produced less emissions overall. But when they delved further, they found that the formation of SOAs didn't drop as steeply as the total emissions coming from the tailpipe.

For instance, when they tested vehicles that slashed primary aerosol pollution by a factor of 20 (compared with the highest emitting vehicles), the amount of SOAs formed dropped by only a factor of 3. When they looked further, they found that the relationship between SOA formation and the emissions was very complicated, and it was affected by the individual compounds formed in the combustion process — even though the effect of only a handful of these individual compounds had been studied. In particular, they found that higher ratios between certain types of organic gases and nitrous oxide compounds (NOx) in the atmosphere (often from tailpipe exhaust) could negate the effects of reduced emissions.  

Using computer simulations for the Los Angeles area, they found that stricter emissions standards may not produce any reduction in SOAs, they reported June 16 in the journal Proceedings of the National Academy of Sciences.

"Overall, we found that new and stricter regulations for gasoline vehicle tailpipe emissions will not be that effective at reducing human exposure to secondary organic aerosol because of changing NOx levels," co-author Robinson said in a statement. "This feedback illustrates the complex coupling between different pollutants, which must be accounted for in models used to develop control strategies."

The findings highlight just how complicated it is to predict and mitigate the negative health effects associated with fuel combustion, because all the chemicals produced may react in complex ways, the researchers noted. As a result, emissions standards should focus on both NOx and organic gases to better control pollution, the researchers wrote in the article.

Originally published on Live Science.

The data, which was collected by sensors on two Google Street View cars, could ultimately help everyone from policymakers to individuals make smarter choices about how to reduce pollution in a given city and increase awareness about how pollution varies in individual neighborhoods, the researchers said.

"The cars drove more than 15,000 miles [24,000 kilometers] in the study domain," said the study’s lead author, Joshua Apte, an assistant professor in the Department of Civil, Architectural and Environmental Engineering at the University of Texas at Austin. "They collected the largest data set ever of air pollution collected by cars driving down the streets of a single city." [In Photos: World's Most Polluted Places]

With such sharp resolution, Apte and his colleagues could see hotspots of pollution, discern any dramatic changes over short distances and tease out specific locations that had consistently good or bad air quality over a long period of time.

The study was the result of a collaboration between the Environmental Defense Fund; Aclima, which develops environmental sensing systems; and Google. The goal was to map and measure pollutants that impact human health and the environment. The results were published online June 5 in the journal Environmental Science & Technology.

Typically, air pollution in urban areas is measured by stationary monitoring sites that are equipped with sensors and are sparsely located around a city. On average, there are one to four sites per 1 million people in an urban area, Apte said. In Oakland, just three stationary monitors capture air quality data for the 78-square-mile (202 square km) city.

The data from these sites is used primarily for regulatory compliance with the Clean Air Act, Apte said. But, it doesn't provide the high-resolution spatial patterns of air quality.

With the mobile method, Apte and his colleagues were able to get 100,000 times the resolution. They accomplished this with Aclima's mobile sensing platform using highly sensitive pollution instruments on the two cars, which drove down the same street an average of 30 times each and collected 3 million measurements of nitric oxide, nitrogen dioxide and black carbon.

Some of the findings were expected, according to the researchers. Busy roads and industrial neighborhoods had higher levels of pollutants than quieter streets in mainly residential neighborhoods. But, a few findings stood out.

First, pollution can change greatly in a small area. There were many blocks where pollution varied by a factor of five or eight from one end of the block to the other, Apte said. There were also lots of hotspots — places less than 330 feet (100 meters) long — where the levels of pollution were substantially higher than what might have been expected. Last, the location of the hotspots stayed consistent over time, the researchers said.

Oakland is a city with industrial and residential zones comingled, which may account for the hotspots, but places like restaurants, car dealers, garages and even some homes showed up as hotspots time and time again, the study found. Until the creation of these new maps, those hotspots had been unknown.

"That's bad news and good news," Apte said.

The bad news is that pollution may be worse than scientists may have anticipated, he said. "The good news is that we may have more ways to reduce exposure to pollution than we might previously have thought," he added.

Apte said there is still a lot of data to sift through, and he expects to draw other conclusions from the pollution map. But, he said he would like to see these mobile monitoring techniques deployed in developing countries, where air pollution is a big problem, but where data is, practically speaking, nonexistent.

"We've just scratched the surface," he said.

Original article on Live Science.

The air pollution around you could affect how well you sleep, a new study finds.

Researchers found that people in the study who lived in areas with high levels of air pollution were 60 percent more likely to sleep poorly, based on the measures used in the study, than those who lived in areas with cleaner air.

Chronic sleep deprivation has been linked with a range of health problems, the study said.

"Not having enough sleep and having low quality sleep affects people's performance, increases the risk of vehicle accidents, lowers mood," said Dr. Martha E. Billings, the lead author of the study and an assistant professor of medicine at the University of Washington. [5 Surprising Sleep Discoveries]

"Over time, there is a higher risk of cardiovascular diseases and cancer in people who are not getting adequate sleep, so there is a lot of implications as well as general well-being and the quality of life," Billings said.

The researchers used data from an ongoing study called the Multi-Ethnic Study of Atherosclerosis (MESA) to look for correlations between exposure to air pollution and the quality of sleep of 1,863 individuals in six U.S. cities. The researchers focused on two measures of sleep quality — sleep efficiency, which is the total amount of time actually spent asleep, and the frequency of awakenings after falling asleep.

The study participants wore actigraphy watches, which are similar to a FitBit. They detected how many times each person woke up during the night and how long they stayed awake, Billings said.

The researchers compared this data set with information about the concentrations of two major air pollutants around the participants' homes. They looked at nitrogen dioxide (NO2) and fine particulate pollution (PM2.5), meaning solid particles in the air that have a diameter of less than 2.5 micrometers. This information came from the Environment Protection Agency's monitoring sites across the U.S. in combination with local environment data and statistical modeling.

The researchers grouped the participants into quartiles based on the level of air pollution in their areas, Billings said. "We found that there was an about 60 percent higher odds of having a low sleep efficiency if you had an exposure in the highest quartile of air pollution."

Low sleep efficiency, as the researchers defined it in the study, meant being asleep less than 88 percent of the time spent in bed. The researchers found that the percentage of people suffering from low sleep efficiency as well as the total amount of time they were awake increased with the concentration of air pollution in their homes.

The study found an association, not a cause-and-effect relationship, between air pollution levels and sleep quality. Billings said the researchers don't know how air pollution may affect sleep, but there are many possible mechanisms in which air pollution could be causing people to toss and turn. [7 Strange Facts About Insomnia]

"It may be because they are exposed to more traffic noise that is disrupting their sleep," Billings said. "It could also be an effect of the air pollution itself that is causing airway irritation. Sometimes those small particles can get into the blood stream and that could affect regulation of sleep in the brain – that's our hypothesis, but we still need further studies to show whether this is really the case."

The average age of the study's participants was 68. Billings said she and her team made sure to adjust for other factors that could affect people's sleep quality, such as body mass, age, smoking or having certain conditions, including sleep apnea or depression.

Air pollution has been linked to the increased risk of respiratory conditions, including asthma and even lung cancer. But recent studies have pointed to the possible association between air pollution and a much wider range of health problems. For example, a study by researchers at the University of Birmingham in the U.K. published earlier this year found that every extra 10 micrograms of PM2.5 per cubic meter of air was linked with a 22 percent increase in risk of dying of any type of cancer in elderly people.

Other research suggests that pregnant women who breathe highly polluted air are more likely to give birth prematurely, according to the Stockholm Environment Institute. A team from the University of Lancaster in the U.K. found air pollution particles in human brains, and said the evidence suggests these particles could contribute to dementia.

Billings and her colleagues presented their new research at the International Conference of the American Thoracic Society earlier this week. The findings have not been published in a peer-reviewed journal.

Originally published on Live Science.

A small innovation could have a big impact on air pollution. In Belgium, researchers have engineered a device that uses sunlight to purify polluted air and produce hydrogen gas that can be stored and used for power.

"We couple both processes together in one device," Sammy Verbruggen, a professor of bioscience engineering at the University of Antwerp, told Live Science. "Hydrogen production on one side and air purification on the other side."

Verbruggenis working with two teams of researchers who had been separately investigating both processes for years. At the University of Antwerp, the scientists had been testing different ways of combing light energy with nanomaterials to purify air. At the University of Leuven, another team had been working on a tiny fuel cell with a membrane that could produce hydrogen gas from water. [In Photos: World's Most Polluted Places]

Now, the two teams have merged their expertise to create this newest device, which could purify fouled air and produce energy at the same time.

Verbruggensaid the researchers are focusing on air polluted with volatile organic compounds (VOCs), which are small molecules produced by chemicals in adhesives, upholstery, carpeting, copy machines, cleaning fluids and more. In sufficient concentrations, VOCs can cause severe headaches, eye irritation, dizziness, nauseaand asthma attacks. 

The small molecules can be found in the air of enclosed buildings that are not well-ventilated, according to the Environmental Protection Agency, which may include newly built high-rises to factories that manufacture goods like paint and carpeting.

"They can lead to a disease called the sick building syndrome," Verbruggensaid.

The prototype cell is a square with an active area that measures about 0.4 inches by 0.4 inches (1 centimeter by 1 cm). At one side of the device, a tube delivers polluted air into the cell. Light enters naturally through a transparent window that covers a membrane treated with a light-activated catalyst. Once polluted air and light meet at the membrane, the catalyst tears apart the small organic molecules.

In the process, protons are set free and seep through the membrane, collecting on the other side. There, a platinum catalyst converts them to hydrogen gas, according to the researchers. Meanwhile, the purified air exits through a second tube.

Verbruggen and his colleagues were able to purify air and create gas from a variety of organic compounds, including methanol, ethanol and acetic acid. The scientists are also conducting new experiments with acetaldehyde, a liquid used in the make acetic acid and perfumes. Verbruggen said the most obvious applications are in industries that produce a waste stream, such as manufacturers of paint or textiles.

"You can purify the waste streams so that they meet their environmental quota and at the same time recover the energy that was stored in those molecules," Verbruggen said. The gas produced could be used to power the lights or other machines in the factory, he added.

At the moment, the team has not come up with an engineering solution to collect and store the gas. That’s another step in the engineering process, and one that will need to be solved by further research and development, Verbruggen said.

"I'm more motivated to improve the cell's performance, right now," he said.

Currently, the membrane responds to ultraviolet rays in sunlight, which is only about 4 to 5 percent of the spectrum. But, if the researchers could modify the materials to make them respond to 40 or 50 percent of the solar spectrum, that would increase the efficiency of the cell as a whole, they said.

"Improving the environment is a driving force for us," Verbruggensaid. "If we can catch two flies at the same time — clean up the environment on one side and also provide a cleaner energy source — that's a net benefit, because there's no extra energy input to drive these reactions, just pure sunlight."

Original article on Live Science.

More than a quarter of deaths in children under age 5 worldwide are tied to polluted environments, such as contaminated water and smoggy air, according to a new report.

The report, from the World Health Organization (WHO), found that each year, 1.7 million children under age 5 die from causes attributable to polluted environments. That's about 26 percent of all childhood deaths in that age group in 2012.

"A polluted environment is a deadly one — particularly for young children," Dr. Margaret Chan, the director-general of WHO, said in a statement. "Their developing organs and immune systems, and smaller bodies and airways, make them especially vulnerable to dirty air and water."

For their body size, children consume more food, drink more water and breathe a greater volume of air than adults, WHO said. In addition, children are more likely to play outdoors and put their hands and other objects in their mouths, and this also increases their exposure to environmental hazards, WHO added.

The report estimated that in 2012:

• 570,000 children under 5 years old died from respiratory infections, such as pneumonia, tied to indoor and outdoor air pollution. Sources of air pollution include smoke from household stoves using unclean fuel (such as charcoal, coal and crop waste), as well as secondhand smoke and emissions from vehicles.
• 361,000 children died due to diarrheal illnesses linked to contaminated water, poor sanitation and poor hygiene.
• 270,000 children died during the first month of life from conditions such as premature birth that were tied to environmental factors, including the mother's exposure to air pollution, contaminated water and poor sanitation.
• 200,000 children died from malaria that could have been prevented through environmental actions, such as reducing areas of stagnant water where mosquitoes breed.
• 200,000 children died from unintentional injuries tied to environmental risks, such as poisoning, falls and drowning.

"Investing in the removal of environmental risks to health, such as [by] improving water quality or using cleaner fuels, will result in massive health benefits," said Dr. Maria Neira, the director of WHO's Department of Public Health, Environmental and Social Determinants of Health.

For example, WHO estimated that a 75 percent reduction in smoke from household cook stoves could reduce cases of child pneumonia by up to 46 percent in certain settings. Interventions to increase access to safe drinking water and improve sanitation and hygiene could reduce diarrheal morbidity in children by up to 45 percent, the organization said.

Government agencies could also work together to improve hygiene at health facilities where women give birth, increase the availability of public transportation to reduce emissions from vehicles and better manage hazardous waste to reduce exposure to harmful chemicals, WHO said.

Original article on Live Science.

ATLANTA — Climate change may have surprising and wide-ranging effects on mental health, experts say.

That's because climate change is both a root cause of mental health crises and a "threat multiplier," meaning that it makes existing mental health problems worse, said Dr. Lise Van Susteren, a psychiatrist in private practice and an advisory board member for the Center for Health and the Global Environment at the Harvard T.H. Chan School of Public Health.

Van Susteren spoke about the connection between climate change and mental health yesterday (Feb. 16) here at the Climate & Health Meeting, a gathering of experts from public health organizations, universities and advocacy groups that focused on the health impacts of climate change. [5 Ways Climate Change Will Affect Your Health]

For example, researchers have documented a link between extreme climate and weather events and higher levels of aggression, Van Susteren said. A 2013 study published in the journal Science found that increases in temperature and extreme rainfall are associated with increased levels of conflict between individuals, and between groups, she said. 

One possible explanation for the link between rising temperatures and aggression is that higher temperatures increase levels of adrenaline in the body, which can contribute to aggression, Van Susteren told Live Science.  

In her talk, Van Susteren also highlighted the link between rising air-pollution levels — which can be caused by rising temperatures — and a higher risk of neurological and psychiatric problems. When a person breathes in particulate matter from air pollution, that matter can enter a person's olfactory nerve and cause neural inflammation, she said.

Neural inflammation is linked to disorders found in all age groups, including Alzheimer's disease and cognitive disorders, she said.

One question that needs to be explored, however, is whether this neural inflammation also causes more conventional psychiatric disorders, such as anxiety and depression, Van Susteren told Live Science.

The American Psychological Association has reported that when pregnant women are exposed to air pollutants, their children are more likely to have symptoms of anxiety and depression, Van Susteren said in her talk. 

In addition, research has shown that the average numbers of emergency room visits for panic attacks and threats to commit suicide are higher on days with poor air quality, Van Susteren said.

But she noted that not all of climate change's effects on health can be easily quantified in studies. "Not everything that counts can be counted," she said. Rather, there are "insidious" effects of climate change that could cause psychological strain on a societal level that will be hard to overcome, she said.  

In one case, a 17-year-old boy in Australia developed such distress over climate change that he wound up hospitalized, Van Susteren said. The doctors who treated him called his condition "climate change delusion" in their report of his case, which was published in 2009 in the Australian and New Zealand Journal of Psychiatry. The boy had refused to drink water because he believed that it would cause millions of people in the drought-ridden country to die.

In her talk, Van Susteren stressed the need to take action on climate change; if action is not taken, she said, it will have profound effects on other children's mental health as well.

Originally published on Live Science.

ATLANTA — Air pollution is one human-made factor that is trapping sunlight and causing climate change, but the relationship also goes the other way: Climate change stands to increase levels of air pollution, experts say.

Although climate change is multifaceted, and won't bring warmer temperatures to all parts of the globe, the average global temperatures will rise.

Research shows that "a warming climate will lead to more severe air pollution," and that this holds true even if the only factor that changes is temperature, said Patrick Kinney, a professor of urban health and sustainability at the Boston University School of Public Health. Kinney's research group has looked into how temperature and air pollution are related. [5 Ways Climate Change Will Affect Your Health]

They've found that "air pollution and climate change are really intimately connected in both directions," Kinney said.

"While we've been damaging the Earth's climate system … we've also been damaging our own health in the process," Kinney said, speaking here today (Feb. 16) at the Climate & Health Meeting, a gathering of experts from public health organizations, universities and advocacy groups that focused on the health impacts of climate change.

"It's a sword that cuts with two very deadly edges, both for climate and for health," Kinney said.

For example, higher temperatures, in particular, will increase smog pollution, Kinney said, in part because smog contains ozone particles, which form faster at higher temperatures.

But air pollution doesn't come only from the obvious human sources, such as cars and factories. Other sources, such as burning forests, also contribute to air pollution, and these factors are also related to climate change, Kinney said. Higher temperatures draw moisture out of the soil and into the air; this dries out the soil and, in turn, dries out the vegetation, making it more vulnerable to wildfires, he explained. 

The smoke from wildfires remains in the air for a long time and can travel long distances, Kinney said. This type of air pollution kills nearly half a million people prematurely every year, worldwide, he said.

Whether it's the burning of wood or the burning of coal, researchers say the pollutants that are released into the air have similar health effects, Kinney noted.

And the negative health effects of air pollution go beyond a scratchy throat or a nagging cough. 

Major health consequences of exposure to air pollution include an increased risk for heart disease and lung cancer, Kinney told Live Science. Air pollution is composed of tiny particles that "act very similarly to cigarette smoke," he said. "We know a lot about how cigarette smoke can cause [health] problems; air pollution is doing the same thing," he added. [8 Ways Global Warming is Already Changing the World]

The links between air pollution and both heart disease and lung cancer may not be obvious to many people because these conditions develop over many years, Kinney said. These links are "more pernicious," he said, adding that the evidence for them has "emerged through careful studies of large populations of people."

The finding that climate change can play a role in increasing air pollution means that air pollution will be "more difficult to control in the future than we thought," Kinney said.

"The fact that we do have clean air [today] is because of the great work that the Environmental Protection Agency has been doing for the last 40 years," Kinney added.

Kinney also discussed the link between climate change and pollen allergies. "Pollen is very climate sensitive," he said.

But the link isn't simply that a warmer climate means a longer pollen season. In addition to the longer season, increased levels of carbon dioxide in the air cause plants to produce more pollen, Kinney said. 

Originally published on Live Science.

A warm blob of water lurking in the Pacific Ocean in 2014 and 2015 led to a spike in ozone levels across the western U.S., new research suggests.

The blob of warm water, which sat about 310 miles (500 kilometers) off the Oregon coast, was linked to a high-pressure system in the atmosphere that resulted in warm, calm air and sunny skies across nearly a quarter of the country, said study co-author Dan Jaffe, an atmospheric scientist at the University of Washington Bothell.

Those atmospheric conditions sped up the formation of ozone in the atmosphere, Jaffe added. (Ozone in the lower atmosphere is harmful to human health, while high in the atmosphere it forms a protective layer that shields the planet from harmful UV radiation.)

The finding suggests that these ocean patterns don't just mess with sea life; their effects may also reach far inland, he said. [The World's 10 Most Polluted Places]

Warm patch

The "blob" ― as meteorologists affectionately called the mass of warm water ― occurred from the winter of 2014 through the summer of 2015, when high sea-surface temperatures prevailed in the Northeast Pacific Ocean. The warmer waters — about 2 to 7 degrees Fahrenheit (1 to 4 degrees Celsius) higher than average for the region — spanned from the coast of Sitka, Alaska, to Santa Barbara, California, and came with a high-pressure system in the atmosphere that led to low wind speeds, fewer storms and sunnier skies.

The warm blob scrambled the food chain and brought a host of strange ecological effects: The toastier waters fueled some of the worst-ever toxic red tide algal blooms, and marine mammals died in droves as they struggled to find enough food in normally cold, food-rich waters, Jaffe said.

But the blob also had stark effects inland. In June 2015, for instance, the average monthly air temperatures were elevated between 1.8 and 10.8 F (1 and 6 C) relative to normal in the western U.S., researchers reported Wednesday (Feb. 15) in the journal Geophysical Research Letters. These regions also experienced more cloud-free, windless days.

Jaffe and his colleagues had been tracking levels of ozone, a compound with three atoms of oxygen that can irritate the lungs, at the Mount Bachelor Observatory in central Oregon.

They found record-high levels of ozone above the Oregon peak. That spurred them to examine levels throughout the Mountain West. Sure enough, they found highly elevated levels of ozone throughout the region. 

"When you looked at where the highest temperatures were and the unusual highest ozone levels were, you see an unusually good match," Jaffe told Live Science.

That made the team suspect the blob may have fueled the ozone levels. Ozone forms when hydrocarbons and nitrogen oxides, which are emitted as pollutants from cars, undergo a complicated chemical reaction with sunlight in the atmosphere. Both sunlight and high temperatures fuel faster ozone-formation, whereas the wind blows away the basic building-block pollutants, making it harder to form ozone, Jaffe said.

When they investigated ozone levels throughout the West, they found areas with the hottest, most stagnant air also had highly elevated ozone levels, compared with historical averages. For instance, Salt Lake City and Sacramento, California, had unusually high levels, likely a combination of having high emissions of the base pollutants, as well as the optimal conditions for forming ozone, Jaffe said.

The new findings suggest the blob directly led to dangerous levels of ozone across the western U.S.

What's not known, however, is whether climate change will lead to more of these blobby weather patterns.

"We know it's getting warmer, and the question becomes how will ozone change in the future?" Jaffe said.

Originally published on Live Science.

ATLANTA — The climate crisis will have significant effects on health, but "we do have solutions at hand," former U.S. Vice President Al Gore said today.

Some of the health risks that Gore, an environmental expert, a book author and a Nobel Peace Prize winner, highlighted in his speech included the spread of infectious disease, the dangers of extreme heat and the health effects of air pollution.

These health risks, and their potential solutions, were discussed here today (Feb. 16) at the Climate & Health Meeting, a gathering of experts from public health organizations, universities and advocacy groups that focused on the health impacts of climate change. [5 Ways Climate Change Will Affect Your Health]

The problems are already here, Gore said, as infectious diseases are now spreading to areas where they previously were not found. In addition, heat stress from extreme heat waves causes more deaths each year in the United States than all other extreme weather events, such as hurricanes and tornadoes, combined, he said. And certain types of air pollution around the world kill about 6.5 million people each year, he said.

"It's hard to focus on some of these horrific consequences of the climate crisis on health, but hope is justified," Gore said in his keynote address. "We are going to win this," he said.

Solutions to combat climate change are readily available, Gore said. Since 2001, the U.S. has significantly increased its wind and solar energy capacities, and goals that were set for 2010 were met and surpassed by then, he said.

In addition, global carbon dioxide emissions have leveled off in the last three years, Gore said. "For the first time in the absence of an economic crisis, there has been no increase" in global carbon dioxide emissions, he said.

And although these emissions are still very high, "we're now at an inflection point and it is going to start going down," Gore said.

Originally published on Live Science.

London may be known for its drizzly weather, but in 1952 the city's quintessential fog cover turned deadly, and no one knew why — until now.

For five days in December 1952, a fog that contained pollutants enveloped all of London. By the time the dense fog cover lifted, more than 150,000 people had been hospitalized and at least 4,000 people had died. Researchers now estimate that the total death count was likely more than 12,000 people, as well as thousands of animals. Despite its lethal nature, the exact cause and nature of the killer fog has largely remained a mystery. Recently, a team of researchers has determined the likely reasons for its formation.

Researchers have for a long time connected emissions from burning coal with the killer fog, but the specific chemical processes that led to the deadly mix of pollution and fog were not fully understood. To determine what turned the fog into a killer, an international team of scientists from China, the U.S. and the U.K. recreated the fog in a lab using results from laboratory experiments and atmospheric measurements from Beijing and Xi’an, two heavily polluted cities in China. [In Photos: World's Most Polluted Places]

Study lead author Renyi Zhang, an atmospheric scientist at Texas A&M University, said that sulfate was a big contributor to the deadly London fog. Sulfuric acid particles, which formed from the sulfur dioxide that was released from the burning of coal, were also a component of the fog. The question was, How did sulfur dioxide get turned into sulfuric acid?

"Our results showed that this process was facilitated by nitrogen dioxide, another co-product of coal burning, and occurred initially on natural fog," Zhang said in a statement. "Another key aspect in the conversion of sulfur dioxide to sulfate is that it produces acidic particles, which subsequently inhibits this process."

The natural fog contained larger particles, Zhang explained, with the smaller acidic particles evenly distributed throughout. When those fog particles evaporated, an acidic-haze was left covering the city.

The 1952 killer fog led to the creation of the Clean Air Act, which the British Parliament passed in 1956. Researchers still consider it the worst air pollution event in European history.

The air of cities in China, which is often heavily polluted, has a chemistry that's similar to the killer fog in London, Zhang and his colleagues found. China has battled air pollution for decades, and it is home to 16 of the world's 20 most polluted cities, according to the researchers. For instance, air pollution in Beijing often far exceeds the U.S. Environmental Protection Agency's acceptable air standards.

The researchers said that the main difference between China's smog and the killer London fog is that China's haze is made up of much smaller nanoparticles. Also, the formation of sulfate is only possible with ammonia, the scientists added.

"In China, sulfur dioxide is mainly emitted by power plants. Nitrogen dioxide is from power plants and automobiles, and ammonia comes from fertilizer use and automobiles," Zhang said. "Again, the right chemical processes have to interplay for the deadly haze to occur in China. Interestingly, while the London fog was highly acidic, contemporary Chinese haze is basically neutral."

A better understanding of air chemistry is key to developing effective regulatory actions in China, Zhang said.

"We think we have helped solve the 1952 London fog mystery and also have given China some ideas of how to improve its air quality," Zhang said. "Reduction in emissions for nitrogen oxides and ammonia is likely effective in disrupting this sulfate-formation process."

The research was published online Nov. 9 in the journal Proceedings of the National Academy of Sciences.

Original article on Live Science.

A stunning, blue-and-green visualization of the globe allows viewers to see the world's wind and weather patterns as forecast by supercomputers around the world.

The striking animation, called "earth," was designed by computer programmer Cameron Beccario, an engineering manager at the computer coding company Indeed Tokyo in Japan. The interactive graphic allows users to toggle between views that show the flow of wind; the movement of ocean currents and the height of waves; the air temperature; and the circulation of air pollutants around the globe. [101 Stunning Images of Earth from Above]

The visualization of Earth draws from the huge assortment of data from myriad instruments floating in the planet's atmosphere, drifting along ocean currents and sitting in the soil. For instance, the model uses the National Centers for Environmental Prediction's Global Forecast System, which uses supercomputers to run a model that predicts weather four times a day. That model uses dozens of different types of measurements, from soil moisture to precipitation to ozone concentration. Other data, like sea-surface temperature, are gathered and updated every day from an array of instruments, including infrared satellites, moored buoys and ships just passing through a region. Carbon-dioxide measurements track the concentration of the greenhouse gas at the Earth's surface.

The visualization recently provided a view of Hurricane Matthew's destructive path, while another clip from "earth" revealed the location of monster waves over the course of a year. Yet another slice of the data reveals the path of the air pollutant sulfate as it traveled over the Pacific. Particulates of sulfate can block sunlight, thereby cooling the planet.

But Beccario hopes people explore the site on their own.

"The site is designed to be fairly sparse because I want visitors to discover their own insights. I think this is much more rewarding than being fed a particular narrative," Beccario said.

The graphic was initially inspired by the wind map, a visualization of wind flowing across the United States created by artists Fernanda Viégas and Martin Wattenberg.

"I thought that would be a great project to emulate and expand upon," Beccario told Live Science. "I've always been interested in science and weather, so this project was a great platform to explore those interests as well. I remembered thinking: What do the winds around Antarctica even look like?! I really wanted to see those patterns." 

Original article on Live Science.

Living close to a site used for hydraulic fracturing, also called fracking, may increase a person's risk of developing asthma, a new study finds.

Researchers found that people who lived close to active fracking wells were more likely to develop mild, moderate or severe asthma compared with those who did not live near active sites, according to the study, published today (July 18) in the journal JAMA Internal Medicine. 

“Fracking" is a shorthand term often used to refer to an unconventional way of getting natural gas out of the ground. (Technically, fracking is just one step in this four-part process.) In the study, the researchers looked at unconventional natural gas development activity in Pennsylvania, where more than 6,200 wells were drilled between the mid-2000s and 2012. [Facts About Fracking]

The researchers looked at patient data from a regional health clinic and identified more than 35,000 patients with asthma in the area. The patients were grouped based on whether their asthma was categorized as mild (meaning the patient was prescribed medication for asthma), moderate (the patient visited the emergency room because of asthma) or severe (the patient was hospitalized because of asthma). Then, the researchers looked at how close these patients lived to sites with different types of well activity.

There are four steps in this type of natural-gas extraction, and each may be linked to an increased risk of asthma for people living nearby, according to the study. The first step is "well pad preparation," a monthlong process during which an area of land is cleared and equipment is brought in. The second step is drilling, which can also last about a month, according to the researchers. The third step is the "stimulation" of the drilled well — this is the actual fracking — and lasts about a week, according to the study. The technique involves injecting pressurized liquid into the wells to extract the natural gas.

By this point in the process, more than 1,000 truck trips have been made to carry supplies to and from each site, the researchers added. The final step in the process is gas production.

The researchers found that people who lived in areas with more well activity were more likely to develop asthma of all levels of severity than those who lived in areas with low levels of activity. In addition, each stage of the unconventional natural gas development process was linked to an increased risk of asthma as the activity level increased, the researchers found.  

However, it's unclear if the associations found in the study are causal, the researchers, led by Sara Rasmussen, an environmental health researcher at Johns Hopkins Bloomberg School of Public Health, wrote in their study. In other words, the researchers do not know if unconventional natural gas development causes asthma.

Dr. John Balmes, a professor of environmental health sciences at the University of California, Berkeley who was not involved in the new study, agreed that the study was not designed to establish a cause-and-effect relationship. The study compared people who live near fracking activity to those who live farther away, at a single point in time. But to establish cause and effect, researchers could follow a single group of people who live in an area where there wasn't previously fracking activity but now there is, over time, he said.

What the study does do is help researchers generate a hypothesis about unconventional natural gas development and asthma, Balmes said. While researchers don't know exactly why fracking and related activities might be linked to asthma, the findings suggests that "we need to learn more," he said. [Asthma: Causes, Symptoms & Treatment]

For example, getting specific measurements about the concentrations of certain air pollutants around wells would be beneficial, Balmes told Live Science. Researchers could look at levels of particulate pollution, such as elemental carbon, which is a marker of diesel exhaust, and nitrogen dioxide, he said.

The researchers cautioned that the study had several limitations. For example, the researchers did not have information on the patients' occupations, which could affect asthma risk, and they did not have data on how long these people were living at their current addresses, the researchers wrote.

But the amount of information that the researchers gathered about the different stages of gas development activity was a particular strength of the study, Balmes said. This is an improvement upon previous studies that looked only at the distances that people lived from wells and these people's health, he said.

Although the researchers did not look at the mechanisms linking unconventional natural gas development and asthma, they noted that the activity has been linked to air pollution, particularly from truck traffic, as well as stress, sleep disruption and reduced socioeconomic status for people in the area, all of which have been linked to asthma.

"I would suspect air pollution and stress" play major roles, Balmes said. Scientists know from other studies that the combination of these two factors has a larger effect on asthma than either factor has on its own, he said. Indeed, there's increased research interest right now in how environmental factors and stress are linked to asthma, he added.

Originally published on Live Science.

Higher levels of air pollution may correspond to higher rates of mental health disorders in kids and teens, according to a new study conducted in Sweden.

Researchers found that, in areas with higher levels of pollution, there were more medications dispensed for psychiatric conditions in children and teens, compared with areas with lower levels of pollution.

"The results can mean that a decreased concentration of air pollution — first and foremost, traffic-related air pollution — may reduce psychiatric disorders in children and adolescents," lead study author Anna Oudin, a public health researcher at Umeå University in Sweden, said in a statement.

In the study, the researchers looked at a national registry in Sweden that lists all medications for psychiatric disorders, such as antipsychotics and certain sedatives, that were dispensed to children and teens in four Swedish counties between 2007 and 2010. The researchers also examined data on air pollution levels in these four counties (the counties were Stockholm, Västra Götaland, Skåne and Västerbotten). [11 New Warning Signs Help Spot Mental Illness in Children]

The researchers found that the higher the levels of air pollution, the higher the rate of medications dispensed for psychiatric conditions in children and teens. Specifically, the rate of medications increased by 9 percent with every 10 microgram per cubic meter increase in nitrogen dioxide.

The new findings add to previous research that has shown links between air pollution and anxiety, perceived levels of stress and mental health conditions in the general population, the researchers said in their study, published June 3 in the journal BMJ Open.

It is not clear how air pollution may affect people's mental health, but it could be that air pollution leads to inflammation and oxidative stress, which in turn may contribute to mental health problems, the researchers said. Some research has also suggested that the brain is vulnerable to ambient particulate matter in polluted air, the researchers said.

However, the new study does not show that there is a cause-and-effect relationship between air pollution and psychiatric disorders, said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City, who was not involved in the study. [5 Controversial Mental Health Treatments]

The association between increased pollution levels and increased levels of dispensed medications for such disorders could also have been explained by other factors such as the high prevalence of the mood disorder called seasonal affective disorder (SAD) in Scandinavian countries such as Sweden, he said.

More research is needed to rule out other factors that could be behind the link shown in the study, Horovitz told Live Science.

Originally published on Live Science.

People typically think about clean or dirty air only when they're outside, but air quality can be a significant problem even indoors. And now, using a new gadget, people can identify pollutants — some smaller than the width of a hair — in their homes, and this could help ward off some illnesses, the device's creators said.

AirVisual — a global team of scientists, engineers and others — is producing the gadget, called the AirVisual Node. The Node's bright and colorful screen can illuminate pollution, temperature, humidity and stuffiness, both indoors and outdoors. The team hopes to change the approach to air-quality collection, said Yann Boquillod, co-founder of AirVisual.

People generally have some understanding of what they're breathing outdoors, because most governments actively monitor the air, Boquillod said. Indoor air, on the other hand, is a "big unknown," he told Live Science. "You spend 80 to 90 percent of your time indoors, so if you are able to actually control your indoor air quality," then you can protect your and family's health, Boquillod said. [In Photos: World's Most Polluted Places]

Using this monitor, "I have the visibility of how much pollution my children are breathing," he said.

Indoor air pollution can come from stove tops, fireplaces and wood products, among other sources, according to the U.S. Environmental Protection Agency (EPA). Burning food, especially, can release contaminant-laden smoke into the air, Boquillod said. The Node can identify these contaminants, which can include microscope particles, or particulate matter, called PM2.5. The "2.5" comes from the diameter of the particle, which is 2.5 micrometers. "It's a very tiny particle, much smaller than a hair," Boquillod said.

The Node can measure particles up to 10 micrometers (PM10) in diameter, which includes dust. Particles smaller than PM10 can be inhaled into the lungs and get past the body's normal defense systems, eventually entering the bloodstream, Boquillod said. This can give rise to health issues like eye, nose and throat irritation, he added. The smallest particles can wedge deeply into the lungs, causing respiratory infections, bronchitis and even lung cancer, according to the EPA.

The Node is able to measure the particles using laser technology, the company said. Inside the Node, there is a fan that sucks in ambient air, a laser that shoots a sharp and precise laser beam, and a photo-sensor under the laser. "Whenever particulate matter passes in front of the photo-sensor, it breaks the laser beam," causing interference that is picked up by the photo-sensor, Boquillod said. "The photo-sensor counts how many times the laser beam is broken."

The device relies on a powerful algorithm that identifies the size and number of particles for each intake and extrapolates data from successive intakes to determine overall air pollution, Boquillod said. In addition to examining particles, the device also measures carbon dioxide levels, which can indicate how well a room is ventilated. The larger the amount of concentrated carbon dioxide there is, the stuffier a room tends to be. [The 10 Most Pristine Places on Earth]

When carbon dioxide levels get too high, "you feel like you are not at the most of your cognitive power," Boquillod said. The Node can measure carbon dioxide concentrations of 400 parts per million (ppm) to 10,000 ppm. When carbon dioxide reaches 1,000 ppm, the environment is confined and needs some fresh air, and when the level rises to 1,500 ppm, people will start to feel poorly, he said. When the level soars to 2,000 ppm, it's time to ventilate and exit, Boquillod said.

The best place to gather air-quality data is wherever you spend the most time, Boquillod said, which could be the bedroom or living room. The Node can also be used to measure air pollution outdoors, though the device needs to be in the shade, away from wind and shielded from rain. The Node can connect to the Internet to send outdoor air-quality measurements to AirVisual, which is planning to consolidate and share the data worldwide.

Revenue generated by the Nodes, which are selling on the crowdsourcing site Indiegogo, will help fund AirVisual's social project to map air pollution around the world. Although governments already collect air-quality data in a number of countries, many other nations are poorly monitored, compromising the health of citizens in those places, Boquillod said.

AirVisual currently offers an app and website that share and forecast global air quality. The group has the same goals as a nongovernmental organization, but wants to be self-funded to increase its efficiency in collecting and distributing data, Boquillod said.

The AirVisual Node sells for $149 and has collected $25,500, or 255 percent of its initial $10,000 goal, on Indiegogo. There are 18 days left in the crowdfunding campaign, and the Airvisual team plans to deliver the gadget in April, Boquillod said.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Severe air pollution is choking China with thick veils of smog, and yesterday (Dec. 7), Beijing issued a red alert — the highest possible — due to poor air quality in the Chinese capital city. Recent satellite images of the country show large hazy clouds covering portions of northeastern China that are so thick they can be seen from space.

The images, taken by NASA's Earth-watching Suomi NPP satellite on Nov. 30, show some of the most severe pollution that cities in eastern China, including Beijing, have seen this year.

Shortly after the satellite photos were taken, country officials issued a code orange air pollution alert, which is the third tier of the four-tiered alert system that indicates "heavy" pollution or an Air Quality Index (AQI) reading between 201 and 300. On Monday, however,  the country's authorities  upgraded the alert to  a "code red," the highest level of alarm. It's the first time China has ever issued a code red air pollution alert, which indicates more than three days of air pollution levels with an AQI greater than 300. Officials have advised millions of the country’s citizens to stay indoors, implemented restrictions on driving and put a ban on outdoor barbeque until the smog dissipates, according to news reports. [In Photos: World's Most Polluted Places]

When the satellite image was taken, there was a high measurement of fine, airborne particulate matter — 666 micrograms per cubic meter of air — according to ground-based sensors at the U.S. Embassy in Beijing. Fine, airborne particulate matter, or particles in the air that are smaller than 2.5 micrometers, are particles in the air that measure about one-thirtieth of the width of a human hair.

Most of these particles result from the burning fossil fuels, such as coal, and biomass, such as wood and agricultural byproducts, according to NASA. Coal, in particular, releases carbon dioxide and sulfur dioxide into the atmosphere when it burns.

Sulfur dioxide mixes with water vapor to create sulfuric acid and other sulfates. When sulfuric acid reacts with water in the atmosphere, the result is acid rain, which can be damaging to the environment, according to the U.S. Geological Survey. Sulfate particles also reflect solar radiation, or radioactive energy from the sun that helps warm the planet, according to NASA.  Reflecting this radiation creates a cooling effect in regions where sulfates are present in the atmosphere. This is different from the effect of greenhouse gases, which absorb solar radiation and create warming effects.

However, while the cooling effect from sulfates might seem like a good thing, many airborne sulfates, especially dimethyl sulfate, are considered dangerous to human health, according to the U.S. Environmental Protection Agency (EPA). Particles smaller than 2.5 micrometers are of particular concern because they are small enough to enter human lungs and have been associated with severe lung damage, EPA officials have said. The World Health Organization (WHO) considers air quality to be safe when levels of particulate matter smaller than 2.5 micrometers are below 25 micrograms per cubic meter of air. The high levels recorded in China from Nov. 30 were more than 25 times the WHO's recommended safety level. 

This week, world leaders, including China’s President Xi Jinping, are in Paris for the United Nations conference on climate change. While China has begun to reduce emissions of sulfates, the country still produces many greenhouse gases that contribute to global warming. The Paris climate summit, which will wrap up on Friday (Dec. 11), aims to establish emissions standards that world leaders hope will help slow the effects of climate change.

Follow Elizabeth Newbern @liznewbern. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Thick smog over Shenyang, a large city in northeastern China, sent air pollution in the city last weekend to levels about 50 times higher than what's considered safe by the World Health Organization (WHO). That level of pollution puts the health of everyone in the city at risk, experts say.

China's industrial cities — as well as industrial cities in many other parts of the world — have long been plagued by high levels of fine particulate matter, which researchers call "PM2.5 pollution." (The particles that make up this pollution are 2.5 microns or less in width.) This pollution is created by vehicle exhaust, coal-fired power plants, burning wood and a number of other sources, and produces a hazy blanket of air.

Over the course of a 24-hour day, the maximum amount of fine particulate pollution that a person should be exposed to is 25 micrograms per cubic meter of air, according to the WHO. Chinese government agencies and the U.S. Environmental Protection Agency (EPA) both put that number a bit higher, saying that people should not be exposed to more than 35 micrograms per cubic meter of air.

But in Shenyang over the weekend, levels reached more than 1,400 micrograms of particulate matter per cubic meter, according to the BBC.

That much pollution is "a big deal," said Dr. Norman Edelman, a senior consultant for scientific affairs with the American Lung Association.

Fine particulate matter is dangerous for human health because the particles are so tiny that they can bypass the body's normal defense systems, such as the mucus membranes that line the mouth and nose. The particles can penetrate deep into the lungs, and sometimes can even pass through the tissue of the lungs and enter the bloodstream, Edelman said. [10 of the Most Polluted Places on Earth]

Particulate pollution is hard to escape because its sources are so prevalent in modern cities and towns. But breathing in these superfine particles damages the respiratory tract, experts say, and it can worsen people's pre-existing conditions and increase the risk of new infections.

"If you look at an area that is subjected to spikes in pollution, you'll see an increase in hospital admissions for lung disease and heart disease," Edelman told Live Science.

People with respiratory conditions such as asthma are particularly susceptible to the adverse effects of air pollution, he said.

But research also suggests that air pollution and heart disease are linked, although this link is less clear than the one between pollution and respiratory problems, Edelman said. One idea is that pollution increases inflammation in the body, which can set off the processes that increase a person's risk of having a heart attack or stroke, he said.

Air pollution isn't a problem only for people who already have heart disease or respiratory conditions. Everyone breathing in Shenyang's highly polluted air could potentially feel the effects of that much pollution, Edelman said. Skin rashes, headaches, coughing, nausea and dizziness are a few of the health effects caused by air pollution, according to the EPA. Over time, the pollution can even lead to cancer, birth defects and nervous system damage, according to the agency.

The surgical masks that some people wear to cover their mouths and noses don't fully protect people from such high levels of pollution, said both Edelman and Janice Nolen, assistant vice president of national policy at the American Lung Association.

"At this level [of air pollution], everybody is at risk — healthy adults, everybody," Nolen told Live Science. Normally, the people most at risk are children, people over 65, people with health problems and those who work or exercise outdoors.

To mitigate the health risks that particulate pollution can cause, people need to clean up the sources of the pollution, Nolen said. That's what the U.S. did in 1970 when it passed key amendments to the Clean Air Act, which regulated air pollution on both the federal and state levels. The bill helped to set up controls for the nation's biggest air polluters, such as coal-fired power plants and diesel engines, and it saved the lives of an estimated 150,000 people every year, according to the EPA.

Cleaning up air pollution takes time, Nolen said, but technologies are available to help reduce the pollution caused by smoke stacks and vehicle engines, for example.

"There are a whole host of steps that we have found can reduce emissions of fine particle pollution and clean up the air," she said.

Follow Elizabeth Palermo @techEpalermo. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Editor's Note: This story was updated on Friday, Sept. 25 at 1:15 p.m. E.T.

The news just keeps getting worse for Volkswagen.

The company may have to recall up to 500,000 diesel cars in the United States and 11 million vehicles worldwide because they emit up to 40 times the allowable levels of air pollutants that are called nitrogen oxides (NOx), The New York Times reported.

The company is now embroiled in a scandal after it was revealed that Volkswagen deliberately turned off the filter designed to trap NOx from the exhaust.

"They just wrote a piece of code that said, 'only turn it on when you're being tested,'" said Jorn Herner, chief of the Research Planning, Administration, and Emission Mitigation Branch of the California Air Resources Board's research division. The breadth and flagrant nature of the cheating has enraged many car owners and has forced the company's CEO to resign. [Hyperloop, Jetpacks & More: 9 Futuristic Transit Ideas]

But the recall has also raised this question: Was it so hard to make diesel cars run with low emissions that the company had to resort to cheating?

It turns out that diesel engines have an inherent trade-off between power, fuel efficiency and clean emissions, experts said.

"You have power, you have energy, you have emissions: You get to choose two of them," said Don Hillebrand, the director of energy systems research at Argonne National Laboratory in Illinois, and the former president of the Society for Automotive Engineers.

In this case, Volkswagen prioritized power and fuel economy over meeting the state and the U.S. Environmental Protection Agency's emissions standards, Herner said.

Gasoline engines

To understand why this trade-off exists, it's helpful to know about the differences between diesel and gasoline combustion engines. The gasoline engines that most American cars use work by igniting a vapor of gasoline and air using a spark plug. When the gasoline-air vapor combusts, it expands and pushes a piston down, producing the torque that turns the wheels and propels the car.

Because gasoline is highly refined, it's composed of a fairly uniform mix of relatively short chains of linked hydrogen and carbon atoms, known as hydrocarbons, Hillebrand said.

"You know exactly what the fuel looks like," Hillebrand told Live Science. "It's fairly easy to know exactly the chemical composition of your exhaust."

With uniform combustion products, it's a relatively simple matter to clean the exhaust. Gas engines use simple catalysts, such as a material like platinum, to bind poisonous chemicals like carbon monoxide, and convert them to harmless substances such as carbon dioxide. (Carbon dioxide is the primary greenhouse gas driving climate change, but is also the harmless substance we exhale whenever we breathe.) Carmakers have become extremely good at cleaning gasoline emissions, Hillebrand said.

"After exhaust comes out of a gasoline engine, the air is actually cleaner than the background air in Chicago," Hillebrand said. [6 Unexpected Effects of Climate Change]

Diesel engines

Diesel engines work differently. Instead of using a spark plug to combust the fuel, a diesel engine compresses a mist of the liquid fuel and air to incredibly high temperatures and pressures — sometimes thousands of degrees Fahrenheit. This pressure-cooker environment is actually what causes the mixture to spontaneously combust.

Because the mixture spontaneously combusts, it's at the perfect pressure and temperature to efficiently burn energy in the fuel. The greater gas expansion causes more powerful compression of the pistons, which produces more torque, Hillebrand said. Big rigs use diesel precisely for this extra towing ability, he said. (To withstand the ultrahigh temperatures and pressures produced in the combustion process, diesel engines must also be made of much sturdier, thicker materials, which is why they can run for hundreds of thousands of miles, Hillebrand added).

Diesel fuel

Diesel fuel is also different from gasoline. The thick, syrupy substance isn't much different from the oil pulled directly from deep underground. Chemically, it's barely refined and contains a mix of much longer hydrocarbon chains and other mystery compounds, Hillebrand said.

Because it's chock full of longer hydrocarbon chains, each gallon of diesel fuel contains more energy. Combining the more energy-dense fuel with its more efficient combustion process, the diesel engine can achieve much higher fuel economy.

But, the trouble is that "it's got chemicals in there and things that will burn that you don't always know what they are," although many of them are rich in sulfur, Hillebrand said.

The old diesel cars that belched stinky, sooty exhaust were spewing lots of this sulfurous particulate matter into the atmosphere. Nowadays, carmakers have gotten very good at trapping this type of air pollutant from diesel exhaust, he said. (Ultra-low sulfur diesel fuel also dramatically reduces these emissions, according to the U.S. Department of Energy.)

Noxious fumes

But Volkswagen ran into trouble when trying to trap another type of pollutant, called NOx. NOx includes a variety of nitrogen and oxygen chemical compounds (such as NO2, NO3, etc.) that only form at high temperatures. NOx reacts with sunlight in the atmosphere and converts into ozone, and ozone is an irritant, Herner said.

"It's what makes your eyes water, it makes your throat hurt, it exacerbates asthma and there are all sorts of cardiovascular problems you can get from it," Herner said.

Diesel cars produce much more NOx than gasoline cars. For instance, when Herner and his colleagues tested emissions from 20,000 2009 and later model passenger cars in Los Angeles, just 0.6 percent were diesel cars, yet they produced a significant fraction of the NOx emissions, and most came from Volkswagens and Audis, he said.

"The temperatures and pressures under which a diesel engine runs the most fuel efficient and the most peppy are also the conditions that will convert the maximum amount of oxygen and nitrogen into NOx," Herner told Live Science.

The United States has moved to sharply curb NOx emissions, and the Obama administration recently proposed even lower ozone standards, which will fuel even further NOx reductions. In Europe, where about half of the cars run on diesel fuel, regulators have instead focused on raising fuel economy and reducing carbon emissions, with the trade-off being dirtier air, Herner said. [The 10 Most Polluted Places on Earth]

Dirty emissions, greater power

Cleaning NOx from diesel fuel is also a challenging process. Because of the fuel's more varied composition and the engine's use of spontaneous combustion, it's not clear exactly when and exactly which compounds have formed, making it trickier to clean up, Hillebrand said.

About a decade ago, before emissions standards were lowered, car companies pursued different strategies for solving this problem.

"Different manufacturers made bets on different technology," Herner said.

Cars built by Mercedes-Benz, for instance, inject an extra fluid called urea to convert NOx into less harmful substances. This approach (called Bluetec) doesn't compromise on fuel economy or power, but it requires a separate tank for the urea, which must be periodically refilled, Herner said.

Volkswagen invested millions to develop a NOx trap instead. The trap soaks up nitrous oxide and nitrogen dioxide like a sponge. Once the trap is full, the system can inject a dose of fuel before releasing exhaust substances. The fuel reacts with the NOx to form benign substances, Herner said. Typically, the filter only runs for about 10 seconds, once every 10 minutes, Herner said. (They may also run their combustion differently at certain points to lower emissions.)

In light of recent revelations, however, it looks like Volkswagen made the wrong bet.

Volkswagen may have resorted to cheating because the NOx trap eats up fuel or reduces the car's pep, Herner said. It's a relatively simple fix to reactivate NOx traps on the recalled cars, he said.

"These vehicles can operate within our regulations," Herner said. "Our priority now is to get them fixed so that they do so."

But Volkswagen owners may end up being disappointed with the more sluggish, gas-guzzling cars they get back, Herner said.

Future technology?

It's likely that cars of the future will include diesel technology that combines clean-emission techniques, power and fuel economy, Hillebrand said. When engineers analyze the diesel-engine combustion process, they have found that there are some pressures and temperatures that produce high levels of soot or NOx. But some temperature and pressure regimes get efficient fuel combustion without producing either pollutant.

Hillebrand's team is developing low-temperature combustion systems that aim to do just that. These systems either precisely time fuel injection or even use gasoline and diesel fuel at different times in the car's operation to hit that sweet spot, he said. These experimental systems, however, need a lot more engineering before they're a marketable solution, he added.

Clearly, the problem of clean diesel engines is extremely challenging, the experts said.

"It's not that it's easy. But that doesn't mean that you cheat," Herner said.

Editor's Note: This story was corrected to clarify that while up to 11 million cars are affected by the emissions cheat algorithm, Volkswagen has not issued an official recall for any cars as of yet. The article also clarified that reduced sulfur emissions are also due in large part to ultra low-sulfur diesel fuels.) 

Follow Tia Ghose on Twitter and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Outdoor air pollution may lead to more than 3 million premature deaths globally per year, according to a new study. About 75 percent of those deaths occur in Asia, the study found.

Air pollutants such as ozone and tiny particles of toxins are linked with heart disease, lung disease and other serious afflictions that have long-term impacts on human health.

"Strokes and heart attacks are responsible for nearly 75 percent of air pollution-related mortality," said the lead author of the study, Jos Lelieveld, an atmospheric scientist at the Max Planck Institute for Chemistry in Germany. A "little over 25 percent is related to respiratory disease and lung cancer."

Calculating the effects of outdoor air pollution on a global scale is challenging. One reason is that air quality is not monitored in some regions, and another is that the toxicity of the particles called "fine particulate matter" can vary greatly depending on their source.

In the new study, Lelieveld and his colleagues estimated the amount of premature mortality from outdoor air pollution by combining models of global atmospheric quality with data from satellites and ground-based networks of sensors, as well as population data, health statistics and other research from public health experts. [10 of the Most Polluted Places on Earth]

"Overall, outdoor air pollution — mostly by fine particulate matter and to a lesser extent by ozone — leads to 3.3 million premature deaths per year worldwide," Lelieveld told Live Science.

The scientists calculated that 75 percent of these deaths occur in Asia, with 1.4 million people dying from outdoor air pollution annually in China, and 650,000 people dying yearly in India. In comparison, they estimated that outdoor air pollution prematurely kills about 55,000 people annually in the United States, and 180,000 people yearly in the European Union.

Of the seven sources of outdoor air pollutants the scientists identified, the biggest killers are fires that people use for heating their homes and cooking, which often burn fuels such as wood and coal. These fires cause about one-third of the premature deaths, according to the study that will be published in tomorrow's (Sept. 17) issue of the journal Nature.

"Residential energy use is an inefficient form of fuel combustion that causes a lot of smoke, and is the foremost source of premature mortality in Asia," Lelieveld said.

The next biggest killer is air pollution from agriculture, such as the ammonia gas that is released when fertilizer breaks down in the environment. Agriculture pollution is responsible for about one-fifth of the premature deaths the scientists analyzed, and agriculture is the leading source of outdoor air pollutants in Europe, Russia, Turkey, Korea, Japan and the Eastern United States, the researchers said.

Other artificial sources of outdoor air pollutants include power plants that make energy from fossil fuels, industrial processes, the burning of wood and other organic materials and land traffic. Together, these cause nearly one-third of all premature deaths due to air pollution, the researchers said. Natural sources of outdoor air pollutants, especially desert dust in the atmosphere, accounted for nearly one-fifth of all premature deaths from air pollution.

Air pollution is usually worse in cities, and the scientists estimated 2 million people in urban areas die prematurely each year due to outdoor air pollution. The researchers added that the global urban population is expected to grow rapidly in the future, increasing from the current 3.6 billion to 5.2 billion by 2050, and they estimated that 4.3 million people would die prematurely annually in cities due to outdoor air pollutants by 2050.[ Earth in the Balance: 7 Crucial Tipping Points]

In a related study that will also published tomorrow, other researchers found that reducing air pollution can improve human health. In fact, up to 1,700 premature yearly deaths were prevented by recent large reductions in fires in the Brazilian Amazon, according the findings detailed in the journal Nature Geoscience. About 15 percent of the Brazilian Amazon was deforested between 1976 and 2010 ─ most of it by burning ─ in order to make way for farms. However, since 2004, Brazil substantially reduced its deforestation rates. An associated drop in fires led airborne particle concentrations during the dry season to decline by about 30 percent, improving air quality.

Computer simulations from Lelieveld and his colleagues showed that if the world's production of air pollution continues as usual, and air quality and emission standards stay unchanged through 2050, there will be moderate increases of the number of premature deaths in Europe and the United States, with most of the increases coming in urban areas.

However, very large increases in deaths are expected in South Asia and East Asia, and the yearly global death toll from air pollution could reach 6.6 million people in 2050, Lelieveld said.

"If this growing premature mortality by air pollution is to be avoided, intensive air-quality-control measures will be needed, particularly in South and East Asia," Lelieveld said. "Our study shows that it is particularly important to reduce pollution emissions from residential energy use in Asia. By reducing agricultural emissions, air quality would also improve, especially in Europe, the Eastern U.S.A. and in Eastern Asia."

Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Fireworks are a beloved tradition of the Fourth of July, but the colorful displays also bring a spike in air pollution, a new study shows.

The researchers analyzed information from more than 300 air-quality monitoring sites throughout the United States, from 1999 to 2013. The researchers looked at levels of so-called fine particulate matter — tiny particles that can get deep into the lungs, and are linked with a number of health problems.

The study found that average concentrations of fine particulate matter, taken over a 24-hour period, are 42 percent greater on July Fourth, compared with the few days before and after the holiday.

The increases in fine particulate matter were highest from 9 p.m. to 10 p.m. on the Fourth. During that hour, fine particulate matter concentrations increased by 21 micrograms per cubic meter (µg/m3), pushing the total concentration close to the U.S. Environmental Protection Agency's limit for a 24-hour period of 35 µg/m3. [50 Fabulous 4th of July Facts: History of Independence]

On a local level, increases in fine particulate matter varied depending on a number of factors, including the weather and the proximity of fireworks to the monitoring site. At one site in Utah, where fireworks were set off in a field next to the air-quality monitoring site, particulate matter concentrations rose 370 percent on the holiday, well above the EPA standard.

Exposure to fine particles, like those found in smoke and haze, is linked with a number of negative health effects, such as coughing, wheezing, shortness of breath, asthma attacks and even heart attacks, stroke and early death, according to the EPA. People at greatest risk for problems from fine particulate matter are those with heart or lung disease, older adults and children.

The findings are "another wake-up call for those who may be particularly sensitive to the effects of fine particulate matter," study researcher Dian Seidel, a senior scientist at the National Oceanic and Atmospheric Administration's (NOAA) Air Resources Laboratory in College Park, Maryland, said in a statement.

The EPA recommends that people who are sensitive to fine particulate matter try to limit their exposure to fireworks, either by watching them from upwind or as far away as possible.

Although previous studies have noted an increase in fine particulate matter following fireworks displays, the new study is the first to quantify the effects of fireworks nationwide.

"We chose the holiday, not to put a damper on celebrations of America's independence, but because it is the best way to do a nationwide study of the effects of fireworks on air quality," Seidel said. "These results will help improve air-quality predictions, which currently don't account for fireworks as a source of air pollution."

States are allowed to exceed the EPA standard for 24-hour fine particulate matter concentrations, if they can show that the spike was due to fireworks displays, or other "exceptional events," the researchers said.

Follow Rachael Rettner @Rachael Rettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Breathing polluted air every day may change a person's brain in ways that end up leading to cognitive impairment, according to a new study.

In the study, researchers examined 943 healthy adults who were at least 60 years old and lived the New England region. The investigators used magnetic resonance imaging (MRI) to look at the participants' brain structures, and compared the images with the air pollution levels in the places where the participants lived.

The researchers found that an increase of 2 micrograms per cubic meter in fine-particle pollution — a range that can be observed across an average city — was linked to a 0.32 percent reduction in brain volume. (Fine-particle pollution is a common type of pollution that comes from car exhaust, among other sources.)

That amount of change in brain volume "is equivalent to about one year of brain aging," said study author Elissa H. Wilker, a researcher in the cardiovascular epidemiology research unit at Beth Israel Deaconess Medical Center in Boston.

In general, a smaller brain volume is caused by the loss of neurons that comes with aging, the researchers said. [10 Things You Didn't Know About the Brain]

That same increase of 2 micrograms per cubic meter of fine-particle pollution was also linked with a 46 percent increase in the participants' risk of having what researchers call "silent strokes," which can be seen on brain scans but don't usually cause symptoms. Such strokes have been associated with poorer cognitive function and dementia, the researchers said.

The researchers found that the people in the study who lived in areas with higher levels of pollution had smaller brain volumes and were also at higher risk of silent strokes compared with the people who lived in areas where the air was less polluted. However, the study was done at one point in time, and Wilker noted that it does not prove there is a cause-and-effect relationship between air pollution and brain changes.

This is the first study to examine a link between air pollution, brain volume and the risk of silent strokes in a population of older adults, the researchers said. Previous studies have examined the relationship between air pollution and the brain in children, but not in older adults, they said.

It is not clear exactly how air pollution may change people's brains, the researchers said. They suspect that air pollution may cause increased inflammation, but the researchers are still trying to understand the link, Wilker said. Previous research has linked markers of inflammation to smaller brain volume, according to the study.

The new results may help the researchers understand "what could be going on between air pollution and serious outcomes like stroke and cognitive impairment," Wilker told Live Science.

The study was published today (April 23) in the American Heart Association journal Stroke.

Follow Agata Blaszczak-Boxe on Twitter. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Tougher air pollution control strategies in California may have resulted in better lung health in children, a new study suggests.

Researchers found that children in California experienced improved lung function as levels of air pollution in the state declined between 1994 and 2011.

"We saw about a 10-percent improvement" in the amount that children's lung capacity grew over a four-year period, said study researcher Jim Gauderman, a professor of preventive medicine at the University of Southern California's Keck School of Medicine in Los Angeles. The researchers looked at children who were examined during the period from 2007 to 2011, and compared them with children examined during the mid-1990s

"We have seen dramatic improvements in air quality in Southern California, and this study demonstrates that it has resulted in substantial improvements in children's respiratory health," Gauderman told Live Science.

In the study, which is published in the March 5 issue of the New England Journal of Medicine, the researchers evaluated more than 2,100 children, ages 11 to 15, living in five communities near Los Angeles, which has been one of the most polluted cities in the United States. [10 of the Most Polluted Places on Earth]

To determine what effect stricter pollution-control laws in California have had on changes in lung development among the state's young residents, the researchers tracked three groups of teens over four-year periods. They measured lung function in one group of children every year between 1994 and 1998; a second group was evaluated from 1997 to 2001, and a third between 2007 and 2011.

Cleaner air, healthier lungs

The data revealed that the air in Southern California got cleaner during the nearly two decades over which the children were evaluated. The findings also suggested that reduced emissions from cars, trucks, trains and ships, along with lower levels of industrial pollutants produced beneficial effects on the teens' lung function.

The results showed that the number of 15-year-olds who had abnormally low lung function decreased from 7.9 percent of children in 1998, to 6.3 percent in 2001, and it fell to 3.6 percent by 2011. Being exposed to cleaner air also led to better lung function in kids with asthma, the analysis found.

Of the four air pollutants monitored during the study, the health improvements seen in the teens were most closely linked to lower concentrations of nitrogen dioxide and particulate matter, whereas the changes were linked to a lesser extent with ozone, Gauderman said.

The researchers looked at 11- to 15-year-olds because the lungs develop rapidly at these ages as teens go through puberty, Gauderman said. People reach their maximum lifetime lung capacity by age 20, and what happens to children's lungs during the teen years is critically important as they transition to adulthood, he explained.

This research offers evidence that efforts to enhance air quality can improve children's lung health in the short term and might also make a difference for those kids later in life. Other studies have shown a link between reduced lung capacity in adults and an increased risk of lung disease, heart disease and premature death, Gauderman said

It's important to note that even though the new study was conducted in Los Angeles, the pollutants evaluated in this study are also high in any urban environment in the United States or around the world, Gauderman said.

There's no reason why similar improvements in lung function wouldn't be seen in children living in other areas of the country where similar pollution control strategies are enacted, he suggested.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Hate thunderstorms? Atlanta may not be for you, as scientists recently found such hot-and-humid metros in the Southeast can birth more summer thunderstorms than rural areas.

In the study, researchers marked the location of every thunderstorm born in northern Georgia and northeastern Alabama during a 17-year period. There were nearly 26,000 thunderstorms detected between 1997 and 2013. The region the city of Atlanta, as well as country hayfields and pastures.

The was a 5 percent greater chance that thunderstorms would pop up over Atlanta compared with the city's surrounding rural areas, the researchers found.

"Per year, that amounts to two or three more thunderstorms of the pop-up variety," lead study author Alex Haberlie, a graduate student at Northern Illinois University (NIU), said in a statement. Pop-up thunderstorms can appear separately from larger storm systems and are more difficult to forecast, Haberlie said.

The storm risk was greatest for urban and suburban Atlanta in the late afternoon and early evening during July and August, according to the study, published Jan. 7 in the Quarterly Journal of the Royal Meteorological Society.

"This study presents the first evidence that urban areas birth or initiate thunderstorms more often than the surrounding rural areas on a climatological timescale," study co-author Walker Ashley, an NIU meteorology professor, said in the statement.

The findings would likely hold up in similar hot-and-humid Southern cities, such as Nashville, Tennessee, and Birmingham, Alabama, Haberlie said. For example, earlier studies have documented that many large cities experienced heavier rainfall than surrounding rural areas. But there are several ways that local factors could control weather patterns over metropolitan areas, the researchers said. Here are some examples:

Pollution: Thunderstorm births were significantly higher on weekdays than on weekend days, the study researchers reported. This suggests higher pollution levels within the city may play a role. (Rural areas showed no significant weekday-weekend differences.)

The heat island effect: The concrete jungle produces heat, often making cities 2 to 5 degrees Fahrenheit (1 to 3 degrees Celsius) hotter than the surrounding countryside. This extra heat means low pressure can form atop urban areas, with higher pressure in rural areas, sparking convection that can trigger thunderstorms.

Tall buildings: Tall buildings may enhance the upward convection that leads to thunderstorms.

Wind direction: More thunderstorms were born downwind of Atlanta, suggesting the prevailing wind direction influenced the location of the storms.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Suicide may be linked to air pollution, according to new research that finds spikes in completed suicides in the days following peak pollution levels.

The research took place in Utah, part of the United States' western "suicide belt." Suicide is the 10th-leading cause of death in the United States; in Utah, it is the eighth. Though the notion that suicide and air quality could be linked may not seem intuitive, similar studies in South Korea, Taiwan and Canada have also linked the two.

Altogether, the findings suggest that suicide "is a preventable outcome, and air pollution could be a modifiable risk factor," said Amanda Bakian, an epidemiologist at the University of Utah and the leader of the new study. [5 Myths About Suicide, Debunked]

Suicide's environmental triggers

Suicide is complicated. Unsurprisingly, mental illness plays a huge role — at least 90 percent of people who die by suicide have a diagnosable mental disorder, according to the American Foundation for Suicide Prevention (AFSP). But a mental disorder alone does not necessarily make a person suicidal, nor do all people who envision committing suicide actually do so. Research suggests that short-term factors in a person's life seem to be important, as suicide is often brought on by an immediate personal or mental health crisis in a vulnerable person, according to the AFSP.  

Some of these short-term factors may be external. It has long been recognized that deaths by suicide peak in the springtime months, which could be a result of social factors. However, a small but growing body of evidence suggests that physical inflammation might also be to blame. Inflammation occurs when the immune system goes into overdrive, triggering the release of a variety of compounds that act on all of the body's systems. The inflammatory compound quinolinic acid has been directly linked to suicidal thoughts, and research has further connected suicide rates with the level of inflammation-promoting particles in the air. For example, a 2013 study published in the journal BMJ Open found that suicides in Denmark went up with tree pollen levels.

Air pollution can cause inflammation as well. A 2010 study in the American Journal of Psychiatry linked suicide with increases in particulate matter in the air in Korea; 2011 research in the Journal of Affective Disorders made the same link in Taiwan. Another 2010 study, this one in Vancouver, found that wintertime emergency room visits for suicide attempts increased in the days following high air pollution levels.

In Salt Lake County, where Bakian and her colleagues are based, winters are marked by air patterns known as inversions, which often trap air pollution close to the ground. They wondered if pollution might be linked with suicides in Utah.

A tentative link

Working with the Utah Department of Health's Office of the Medical Examiner, Bakian and her team gathered data on all suicides in Salt Lake County between 2000 and 2010, a total of 1,546. They chose to focus only on completed suicides, not suicide attempts, because the demographics and characteristics of people who complete suicide and people who attempt suicide are different. (Men are more likely than women to complete suicide, for example, and people who die by suicide use more lethal means, such as guns, than people who survive an attempt.)

The researchers then compared the timing of these suicides with air pollution levels, including fine and coarse particulate matter, nitrogen dioxide and sulfur dioxide from Environmental Protection Agency (EPA) monitors in the county. They found that suicide risk went up two to three days after levels of fine particulate matter and nitrogen dioxide rose.

"The finer the particulates, the better they are at permeating thoracic airways," Bakian told Live Science. The study is the first to examine the link between nitrogen dioxide and completed suicides.

Surprisingly, the link between the levels of these pollutants and suicide was strongest not in the winter, but in the spring and fall.

"What it makes us think is that air pollution interacts with other spring and fall risk factors for suicide," Bakian said. [Suicide: Red Flags & How to Help]

The link was also strongest in men and among the 25- to 64-year-old age group, as well as among those who died by violent means such as firearms, the researchers reported Feb.10 in the American Journal of Epidemiology.

Bakian and her colleagues are interested in researching what might make some subgroups more vulnerable to the effects of air pollution than others. But everyone agrees that more work is needed.

"It is worth highlighting that this is only one study in an area where there is only a small body of research," said André Gagnon, a spokesman for Health Canada, the public health department of the Canadian government, where the Vancouver study was done. "These findings should, therefore, be interpreted cautiously."

Most importantly, Gagnon noted, the research can't establish that the air pollution caused the increase in suicides; it shows only a correlation between the two. In an editorial accompanying the new study in the American Journal of Epidemiology, University of Queensland researchers Yuming Guo and Adrian Barnett noted that the findings bolster the small body of research linking suicide and pollution, but that questions remain.

For example, the researchers controlled for the level of sunlight during the study period, which might affect suicide risk, but they did not control for precipitation directly. Rain or snow alone could influence suicidal behavior, and might also wash pollution from the skies, Guo and Barnett said. 

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

One of the deadliest tornado outbreaks in U.S. history was strengthened by smoke from burning farmlands in Central America, a new study suggests.

On April 27, 2011, some 200 terrifying twisters touched down across the Southeast — the most on record in a single day. Damages topped $11 billion, and 316 people died. (The devastation on April 27 was the worst of a four-day tornado outbreak spanning April 25 through April 28.)

The hardest hit states were Mississippi, Alabama, Tennessee and Georgia, which were struck by 15 tornadoes ranked EF-4 or higher on the Enhanced Fujita Scale. There were also four powerful EF-5 tornadoes — the highest possible tornado ranking — as severe storms raked through these states. [Destructive U.S. Tornadoes of April 2014: Gallery]

Researchers now say that air pollution intensified this incredible tornado outbreak. When supercell storms on April 27, 2011, mixed with smoke in the air, the volatile combination boosted the conditions that trigger tornados, according to a study published Jan. 26 in the journal Geophysical Research Letters.

However, the study notes that the twisters were primarily caused by the storms, not by smoke. "The smoke is not responsible for this outbreak," said Pablo Saide, lead study author and a postdoctoral researcher at the University of Iowa's Center for Global and Regional Environmental Research. "The main driver is the environmental conditions — the temperature and the wind profiles."

During the tornado outbreak, a satellite recorded high levels of smoke drifting across the Gulf of Mexico from burning fields in eastern Mexico and the Yucatan Peninsula. (Pollution from agricultural burning is also a concern in the United States, where several states have regulated the practice under the Clean Air Act of 1990.)

The pollution included soot and aerosols, which are fine particles and droplets suspended in the air. In the new study, the researchers looked at what effects these pollutants may have had on the birth of tornadoes, using a climate model. The researchers found two main effects, which required aerosols to be both close to the Earth's surface and above the cloud layer, Saide said.

One effect was that the aerosols brightened clouds in a way that increased wind shear (vertical differences in the speed and direction of the wind) and lowered the cloud base. The second effect was that the dark soot in the smoke warmed cloud tops, just like the sun does to a dark car. This effect boosts temperature contrasts between the top and bottom of the storm clouds, making it harder for different layers of air to mix. All of these factors tend to make tornadoes stronger and more likely to develop, Saide said.

About 90 percent of the supercell storms on April 27 produced at least one tornado, compared with the typical rate of about 25 percent, according to a study published in July 2014 in the Bulletin of the American Meteorological Society. 

Climate scientist James Elsner, who was not involved in the research, said the study is provocative, but he noted that some effects attributed to the pollutants could actually be independent of aerosols. "I think the increased wind shear is certainly reasonable, but cloud heights are always pretty low across Mississippi and Alabama, so that seems pretty dubious," said Elsner, a professor at Florida State University in Tallahassee who recently published a study on tornado clusters.

The researchers now plan to test their model on other historical tornado outbreaks. "Clearly, we need to know if this is more robust," said study co-author Greg Carmichael, a professor of chemical and biochemical engineering at the University of Iowa.

Testing the effects with climate models that add smoke to large-scale storm simulations could further explain how aerosols enhance tornadoes, said Victor Gensini, a severe-storms climatologist who was not involved in the study.

"This is just one case, but it could definitely be a piece of the puzzle in creating the environment that you need for a tornado," said Gensini, an assistant professor at the College of DuPage in Illinois.

Editor's note: This story was updated Feb. 5 to correct the spelling of Victor Gensini's name.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science .

LAS VEGAS — Companies from around the globe are debuting technologies here at CES that aim to remedy today's most pressing environmental problems.

Some of the biggest names in tech announced that they're embracing more eco-friendly designs for their products. For instance, Samsung introduced a computer monitor made of 30 percent recycled plastic that runs on less energy when it's not in use than conventional monitors. Electronics company LG announced a whole line of "greener" home appliances that use less energy and water than the company's previous models, and Mercedes announced a new luxury vehicle powered by hydrogen fuel cells.

Lots of small companies are getting in on the action too, introducing products — from solar-charging stations to pollution sensors — that put the environment first. Here are some of the coolest green tech products being showcased at CES. [5 Ways Your Tech Will Go Green in 2015]

ecoATM

EcoATM is a stand-alone machine (it looks kind of like a RedBox or CoinStar machine) that allows users to exchange old electronics for cold, hard cash. While it's not exactly new (the first ecoATM launched in 2009), this product was a hit this year at CES, where onlookers crowded around to watch the machine assess the value of beloved smartphones.

The electronics that ecoATM reclaims can be mined for the valuable and rare metals they contain. By recycling your old devices, you can prevent toxic mining waste from being poured into the environment, according to the company. And by keeping electronics out of the garbage dump, you also prevent the toxic materials found inside these devices (things like mercury and cadmium) from leaking into the ground.

Of course, not all of the electronics that find their way into the ecoATM are actually taken apart and used for parts. Most of them are resold to new owners, a company spokesperson told Live Science. (Photo Credit: EcoATM)

Automatic

Automatic lets you harness the computing power of your car for the sake of fuel efficiency. This little device plugs into the diagnostic port of your vehicle, which is typically tucked between the dashboard and the brake pedal. Once plugged in, Automatic connects the car's computer system to your smartphone, relaying data about all of your car's subsystems — from the gas tank to the engine.

With this data at the ready, the device can tell you when there's something wrong with your car before it becomes a major issue, a company spokesperson told Live Science. It's like preventative health for your car, she said, letting you diagnose a problem before it starts eating away at your fuel efficiency or increasing your emissions. [Top 10 Emerging Environmental Technologies]

In addition to letting you know when there's something wrong with your car, Automatic also notifies you when there's something wrong with your driving. If you tend to accelerate too quickly, Automatic will inform you that this bad habit wastes gas. In fact, the company claims that the device can help you spend up to 33 percent less on fuel each year just by getting you to avoid a few gas-guzzling habits. (Photo Credit: Automatic)

Tzoa

Tzoa is a portable environmental sensor that tracks everything from air quality and ultraviolet radiation to humidity and temperature. You can place Tzoa on a side table and let it monitor the air in your living space, or you can clip it to your backpack and it'll measure UV exposure as you walk along the city streets.

The purpose of the device is to help put people in touch with their environment, according to Kevin Hart, Tzoa's co-founder. Users are encouraged to get outside and map air pollution in their communities. This data can then be shared with other Tzoa users via the company's app, Hart told Live Science.

"By crowdsourcing data on to public maps, we can locate chronic issues in our communities and take action against sources of harmful issues," Hart said. "Overall, we believe that awareness leads to advocacy, which leads to action — and that will perpetuate green technologies."

Tzoa users who want to get more involved in environmental advocacy can sign up for the company's ambassador program, an effort that promotes environmental stewardship in communities across the globe. (Photo Credit: Tzoa)

Misfit Shine

The fitness and lifestyle company Misfit announced a new product at CES: the Swarovski Shine. This fitness and sleep tracker was designed in collaboration with jewelry giant Swarovski and features a large blue-hued crystal embedded with sensors. Customers can buy a pendant necklace or wristband to store this attractive wearable, which has one surprisingly green feature: it's solar-powered.

Not all versions of the Shine run on sunlight, just the blue-colored wearable, which Misfit has dubbed an "energy harvesting crystal." The clear crystal version of the Shine can't absorb quite as much light as the blue version, which is why it needs a traditional battery. (Photo Credit: Misfit)

Solpro

Of course, the Misfit Shine isn't the only product at this year's CES that gets its power from the sun. Solar tech company Solpro unveiled its new solar-powered phone-charging device, the Helios Smart, this week, as well.

The device is a pocket-size rectangle that unfolds to reveal three solar panels. These panels can absorb enough sunlight in 90 minutes to charge a standard smartphone, according to the company. The Helios is ideal for those who are on the go and don't feel like hunting for a charging station, or those who are living off the grid (even if just on a camping trip). But Solpro CEO Bill Pike thinks the device is a good solution for everyday charging, as well.

"It won't be just for camping and emergencies," Pike told Live Science in an email. People want alternative, sustainable options for generating energy, he said. (Photo Credit: Solpro)

Follow Elizabeth Palermo @techEpalermo. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science

This Behind the Scenes article was provided to Live Science's Expert Voices: Op-Ed & Insights in partnership with the National Science Foundation.

Cyanobacteria, also known as blue-green algae because of their color, have endured for more than 2.5 billion years, providing ample time to adapt to changes in the Earth's biosphere. They live in water where a diet heavy in nitrogen and phosphorus, combined with global warming, can prompt them to produce slimy toxic blooms that make the water unfit for drinking, agriculture and recreation.

"Human activities have dramatically increased nitrogen and phosphorus inputs into many rivers and lakes, causing algal blooms that threaten economic and recreational uses of those waters," says Hans Paerl, professor of marine and environmental sciences at the University of North Carolina-Chapel Hill Institute of Marine Sciences. "This nutrient over-enrichment in freshwater has led to a global proliferation of cyanobacterial blooms which foul the water, disrupt food webs, reduce oxygen, and produce metabolites toxic to fish, zooplankton, cattle, domestic pets and humans.''

Humans who drink the water or eat its fish or shellfish can suffer damage to the liver, intestines and nervous system. Moreover, while still unknown, the possibility exists that "using this water for irrigation of edible crops could potentially lead to toxins being transferred into consumable foods, since they don't break down easily," Paerl says.

The major sources of nitrogen and phosphorus that enter these water systems and feed the cyanobacteria include runoff from chemical fertilizers, factories, urban impervious surfaces and waste water treatment facilities, and air pollution from fossil fuel and automobile combustion to create "a perfect soup'' of noxious blooms, he says, adding: "We are now having to pay back Mother Nature for all those cultural advances."

Paerl currently is leading an international team of researchers working to better understand and help restore the ecosystem balance in Lake Taihu, the third largest lake in China, a once pristine lake where severe toxic blooms now grow regularly, and which serves as a major source of drinking water for more than 10 million people. "So, the stakes are huge," Paerl says.

Research with a Global Impact

Beyond China, however, insights gleaned from their research almost certainly will have an impact on the management of global waterways, including in the United States, where harmful cyanobacterial blooms resulting in tainted water cause an estimated annual loss of more than $2 billion, according to Paerl and his research colleagues. They threaten some of the world's largest lake ecosystems, including the Great Lakes, and Lakes Okeechobee and Pontchartrain in North America, as well as the large lakes of Africa, Asia and South America.

"Lake Taihu serves as a looking glass for large lake ecosystems threatened by proliferating cyanobacterial blooms,'' he says. "While events in China may seem half-way-around-the-world relative to local concerns, they are in fact a potential foreshadowing for North American waterways."

The Lake Taihu work includes two collaborative projects funded by grants from the National Science Foundation totaling about $2 million.

One major goal of the research is to determine a nutrient threshold, that is, the level of nutrients in a body of water that would prevent toxic blooms from developing. The aim is to know how much to reduce those nutrients, nitrogen in particular. "It turns out we've done a good job reducing phosphorus, but have not been paying enough attention to nitrogen,'' Paerl says. "We are now literally drowning in nitrogen entering our waterways from land and the atmosphere."

Climate Change is Making Things Worse

Climate change is complicating the calculations, since the microorganisms seem to thrive in warm temperatures. "Cyanobacteria love warm weather," Paerl says. "Many of the cyanobacterial blooms typically occur in summertime. Warmer weather will increase the probability that these blooms will become dominant."

Thus, nutrient thresholds likely will need to become lower as the weather becomes warmer. "If you get below a certain threshold, the chances for these blooms to dominate decreases," he says. "But if you increase the temperature at the same time, then the threshold will change too. So we might have to reduce the threshold even more. We are designing a nutrient reduction strategy for whatever the temperature is going to be now, but we may need to revisit the strategy and crank down on the nutrients even more in the future."

The scientists' experiments involve collecting lake water from different locations and adding nutrients in different concentrations to transparent containers, which vary in size from a few liters (microcosms) to more than 1,000 liters (mesocosms), while leaving others untouched to serve as controls for comparative purposes. "We compare the growth in the nutrient additions to the controls, then put the containers back into the lake," Paerl explains, adding that setting up the experiment occurs over several hours on the same day.

"Over time, we monitor algal growth and compare the stimulatory effects of nitrogen and phosphorus, taking into account all the other environmental factors that can control growth like light and temperature,'' he continues. "We conduct these experiments over periods ranging from a few days to several weeks. From that, we can estimate the growth potential of these nutrients over a range of concentrations reflecting varying levels of enrichment from the watershed."

The team also is conducting experiments "where, instead of adding nutrients, we remove them by adding artificial lake water that is missing the nutrients,'' he says. "The idea is to predict what will happen when we reduce nutrient inputs to the lake."

Finally, the researchers are also trying to characterize the organisms already in the water because "we want to know who the players are,'' he says. "The reason we are interested in that is because we need to know how the microbial diversity is changing in the lake.

We want to encourage the growth of good as opposed to bad players. It's not just that these blooms are ugly and discourage tourists, but they produce toxins and more than 10 million people use the lake for drinking water."

Bacteria Not Algae

Despite the misnomer "blue-green algae," cyanobacteria are not algae, but bacteria. They are prokaryotic, meaning they lack a nucleus, unlike traditional algae. Cyanobacteria perform photosynthesis just like traditional algae, but they prefer warm conditions, unlike true algae groups, which reach peak growth rates at lower temperatures.

 "Cyanobacteria are unique in that they are the only bacterial group capable of oxygen-evolving photosynthesis." Paerl says. "This has had major ramifications for evolution of life on Earth, in particular oxygenation of the atmosphere, starting some two billion years ago. This transformation has provided opportunities for higher plants and animals, including human, to inhabit our planet. So, the influence of cyanobacteria on Earth is two-sided from a human perspective — both good and bad."

The researchers depicted in Behind the Scenes articles have been supported by the National Science Foundation, the federal agency charged with funding basic research and education across all fields of science and engineering. See the Behind the Scenes Archive. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.