Millions of tiny pieces of plastic are swirling around in Earth's atmosphere and traveling across entire continents, according to a new study. This environmental problem is likely to get much worse and could have serious effects on human health, experts say.
Microplastics measure less than 0.2 inches (5 millimeters) long, according to the National Oceanic and Atmospheric Administration (NOAA). And previous studies had shown that these microscopic particles can be found in the ocean, bottled water and even our poop, but until now, the atmospheric section of this "plastic cycle" had been poorly understood.
The new study revealed thousands of tons of microplastics already in the atmosphere, with roads as the biggest contributor. Computer modeling also revealed how particles get transported vast distances across the globe and showed that nowhere is safe from the pollution.
The researchers said their findings highlight that microplastics are one of the most pressing environmental issues of our time.
"Microplastics have the capacity to disrupt nearly every ecosystem, not to mention human health," lead author Janice Brahney, an environmental scientist at Utah State University, told Live Science. "We are really only starting to understand the scope of the pollution, never mind the impacts."
In terms of importance, the issue is right up there with climate change and is somewhat intertwined with it, "since plastics are a product of fossil fuels," Brahney said.
Entering the atmosphere
To figure out how microplastics are being transported into and across the atmosphere, Brahney and her colleagues measured the fallout of particles from the air, as a result of both gravity and rain, at sites across the western United States over a 14-month period. Based on their findings, they estimated that around 1,100 tons (1,000 metric tons) of microplastics are in the atmosphere above the western U.S.
The team was "absolutely shocked" by the levels of microplastics they found, Brahney said.
The researchers had predicted that cities would be the largest source of atmospheric microplastic pollution, but the analysis of the plastic showed that roads were the biggest culprit, responsible for 84% of atmospheric microplastics.
"When you consider that plastic, like dust, needs to enter the atmosphere from some physical force, this makes more sense," Brahney said. "Roads — and, more importantly, cars driving on roads — provides the mechanical energy to move particles into the atmosphere."
Other sources included the oceans (11%) and agricultural soil dust (5%), both of which involved strong winds pushing particles into the air. However, the researchers suspect that all three of these sources will likely contribute to differing levels of pollution in other parts of the world.
Circling the planet
Using the data they collected, the researchers created computer models to figure out how microplastics are transported across the planet and which areas are likely hotspots for the highest levels of microplastics, such as Europe, Eastern Asia, the Middle East, India, and the United States.
"The atmosphere is one of the reasons why microplastics are so widespread," Brahney said. "It has the potential to transport plastics to disparate locations, across continents and to really remote locations that would otherwise be untouched by human pollution."
The researchers discovered that the plastic particles could remain in the air for between one hour and 6.5 days. That upper limit is enough time for cross-continental transportation, which means even places like Antarctica are at risk of pollution despite having no direct sources of plastic.
"No one is protected from this source of pollution," Brahney said. "We can ship our garbage to other countries, but it will just come back to haunt us."
The issue of microplastics in the atmosphere is also likely to get much worse.
"Plastic needs some time to break down into the tiny fragments we see in the atmosphere," Brahney said. "Since we don't have effective means for handling plastic waste, and the problem is compounding, it may be that more plastics end up in our environment in the future and, therefore, our atmosphere."
Another important avenue of research, Brahney said, is to figure out how airborne plastics can affect human health.
"Inhaling any particle can have negative health consequences," Brahney said. "But at present, we don't know whether plastics are more or less harmful than other natural aerosols."
The study was published online April 12 in the journal Proceedings of the National Academy of Sciences.
Originally published on Live Science.
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Harry is a U.K.-based senior staff writer at Live Science. He studied marine biology at the University of Exeter before training to become a journalist. He covers a wide range of topics including space exploration, planetary science, space weather, climate change, animal behavior, evolution and paleontology. His feature on the upcoming solar maximum was shortlisted in the "top scoop" category at the National Council for the Training of Journalists (NCTJ) Awards for Excellence in 2023.