Fuels high in ethanol may pose an equal or greater risk to public health than regular gasoline, new findings suggest.
''Ethanol is being promoted as a clean and renewable fuel that will reduce global warming and air pollution,'' said Stanford University atmospheric scientist Mark Jacobson. But he found the number of deaths and hospitalizations linked with respiratory ailments might increase if every vehicle in the United States used the latest automotive technology and ran on fuel containing high levels of ethanol.
The findings counter the environmentally friendly image of ethanol fuels. Ethanol is made from corn and other plants, which naturally soak up carbon dioxide. Research suggests that ethanol production and consumption might therefore release less of this greenhouse gas into the atmosphere than gasoline use does.
Increase in ozone
Jacobson used 3-D atmospheric computer models to simulate air quality in the year 2020, when ethanol-fueled vehicles could become widely available in the United States.
''The chemicals that come out of a tailpipe are affected by a variety of factors, including chemical reactions, temperatures, sunlight, clouds, wind and precipitation,'' he explained. ''In addition, overall health effects depend on exposure to these airborne chemicals, which varies from region to region.
Jacobson focused especially on Los Angeles, which is home to about 6 percent of the nation's population and has historically had some of the most polluted airs in the United States and has been the testbed for nearly all U.S. air pollution regulations, making it ideal for a more detailed study, he explained.
He programmed the model to compare two future scenarios—one in which all the cars, trucks, motorcycles and other autos in the country are fueled by gasoline, and another in which vehicles are driven by E85, a popular blend of 85 percent ethanol and 15 percent gasoline.
''We found that E85 vehicles reduce atmospheric levels of two carcinogens, benzene and butadiene, but increase two others, formaldehyde and acetaldehyde,'' Jacobson said. ''As a result, cancer rates for E85 are likely to be similar to those for gasoline. However, in some parts of the country, E85 significantly increased ozone, a prime ingredient of smog.''
200 more deaths per year
Specifically, E85 would cause ozone levels to increase in Los Angeles and the northeastern United States but to decline in the southeast United States. This is because of levels of airborne pollutants such as nitrogen oxides or volatile organic compounds such as formaldehyde vary in the air of each locale. Emissions from E85 would therefore react chemically in different ways, creating ozone at some areas and destroying it in others.
Gasoline currently leads to roughly 10,000 premature deaths in the United States annually from ozone and particulate matter, Jacobson explained.
''In our study, E85 increased ozone-related mortalities in the United States by about 200 deaths per year compared to gasoline, with about 120 of those deaths occurring in Los Angeles,'' he said. ''These mortality rates represent an increase of about 4 percent in the U.S. and 9 percent in Los Angeles above the projected ozone-related death rates for gasoline-fueled vehicles in 2020.''
"We found that nationwide, E85 is likely to increase the annual number of asthma-related emergency room visits by 770 and the number of respiratory-related hospitalizations by 990,'' Jacobson said of his findings, detailed in the April 18 online edition of the journal Environmental Science & Technology. ''Los Angeles can expect 650 more hospitalizations in 2020, along with 1,200 additional asthma-related emergency visits.''
Combustion engine problem
These numbers might change if better ways to treat ethanol fuel emissions develop in the next 10 years, Jacobson said. "But based on what we currently know, ethanol is at least as bad to public health as gasoline, and possibly worse," he told LiveScience.
"People might say that these aren't huge increases in deaths we're seeing here," he added. "My response would be that I don't think 10,000 deaths a year from gasoline is a good thing to begin with. There are technologies we can use instead of any type of combustion engine that would result in no tailpipe deaths, such as battery-electric vehicles whose energy can come from wind or solar power."
Atmospheric chemist Roger Atkinson at the University of California, Riverside noted, "It's been known for a long time that E85 is not the cleanest fuel in the world." He added that regulatory agencies such as the Environmental Protection Agency and the California Air Resources Board "will have to keep on top of this issue to make sure things don't go awry."