According to a study by Mark Jacobson, a Stanford University civil and environmental engineer, switching from gasoline powered vehicles to ethanol may create poorer quality air, leading to more smog-related deaths. The study was published in an online edition of the peer-reviewed journal, Environmental Science and Technology.

The report claimed that nearly 5,000 people die each year from respiratory problems caused by ozone. Ethanol use would increase ozone levels in some parts of the country that already have high levels and result in about 200 additional deaths per year.

Not everyone agreed. Roland Hwang, of the Natural Resources Defense Council, said ethanol cuts greenhouse gases and reduces one of the key ingredients in the formation of ozone. According to Hwang, Jacobson’s conclusion is an unworkable provocative concept.