Ethanol-powered vehicles are being promoted by everyone from corn growers to President George W. Bush as a way to reduce U.S. dependence on foreign oil and curb global warming. But a new study of the health effects of substituting ethanol for gas reveals a downside: more sickness and death from a nasty air pollutant, ozone.
Because plants sop up carbon dioxide, running cars on ethanol produced from corn or other plants could slow down the rise in atmospheric levels of this greenhouse-warming gas. But Stanford University atmospheric chemist Mark Jacobson wondered what would happen to air pollution if, by 2020, gasoline-powered vehicles were replaced with ethanol cars and trucks. To find out, he ran a computer model that simulated the pollutants produced across the country by vehicles burning a mixture of 85% ethanol and 15% gasoline. The model took into account regional weather patterns, because weather influences which air pollutants form.
Cancer-causing compounds were a wash; there would be an uptick in some but a reduction in others that overall balanced out. Not so for ozone, a lung-searing gas that contributes to smog and is especially harmful to asthmatics and the elderly. Under the 85% ethanol scenario, levels of so-called "reactive organic gases," which can react with other chemicals to form ozone, would rise significantly. This wouldn't matter in the southeast, where natural organics from forests swamp out the effects of the emitted organics and decreased levels of nitrogen oxides would actually reduce ozone. But in the northeastern U.S. and Los Angeles, the rise in reactive organic gases would lead to more ozone.
When Jacobson took into account ozone's health effects and 2020 population projections, he found that annual U.S. deaths from ozone would rise by 185, a 4% increase compared to if we stuck with gasoline-powered cars. There would also be 1200 more asthma hospital visits and 990 hospitalizations for respiratory illnesses. The brunt of these effects would be felt in Los Angeles, which would experience 120 more ozone-related deaths--a rise of 9%. Jacobson's results appear online today in the Environmental Science & Technology.
So what should we do? Jacobson says we should forget about ethanol and instead focus on promoting electric cars and fuel-cell vehicles that run on hydrogen produced with wind or solar power. But Daniel Kammen of the University of California, Berkeley, an expert on renewable energy, says that while the study is "a good first cut," it's unlikely that all vehicles will be running on 85% ethanol by 2020--especially in California, where in January, Governor Arnold Schwarzenegger ordered cuts in carbon emissions through the use of a range of fuels, including hydrogen and electricity. "I think what we're likely to see is quite a different overall mix of fuels," Kammen says.