Ethanol is widely touted as an eco-friendly, clean-burning fuel.
But if every vehicle in the United States ran on fuel made primarily from ethanol instead of pure gasoline, the number of respiratory-related deaths and hospitalizations would likely increase, according to a new study by Stanford University atmospheric scientist Mark Z. Jacobson. His findings are published in the April 18 online edition of the journal Environmental Science & Technology (ES&T).
''Ethanol is being promoted as a clean and renewable fuel that will reduce global warming and air pollution,'' said Jacobson, associate professor of civil and environmental engineering. ''But our results show that a high blend of ethanol poses an equal or greater risk to public health than gasoline, which already causes significant health damage.''
Gasoline vs. ethanol
For the study, Jacobson used a sophisticated computer model to simulate air quality in the year 2020, when ethanol-fueled vehicles are expected to be 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. Ours is the first ethanol study that takes into account population distribution and the complex environmental interactions.''
In the experiment, Jacobson ran a series of computer tests simulating atmospheric conditions throughout the United States in 2020, with a special focus on Los Angeles. ''Since Los Angeles has historically been the most polluted airshed in the U.S., the testbed for nearly all U.S. air pollution regulation and home to about 6 percent of the U.S. population, it is also ideal for a more detailed study,'' he wrote.
Jacobson programmed the computer to run air quality simulations comparing two future scenarios:
- A vehicle fleet (that is, all cars, trucks, motorcycles, etc., in the United States) fueled by gasoline, versus
- A fleet powered by E85, a popular blend of 85 percent ethanol and 15 percent gasoline.
Deaths and hospitalizations
The results of the computer simulations were striking.
''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.''
Inhaling ozone-even at low levels-can decrease lung capacity, inflame lung tissue, worsen asthma and impair the body's immune system, according to the Environmental Protection Agency. The World Health Organization estimates that 800,000 people die each year from ozone and other chemicals in smog.