Methanol, like ethanol, is an alcohol used as an alternative fuel or gasoline additive. But it is poisonous to humans and animals when ingested. It is most often produced using natural gas, but it can be made using biomass, such as wood. According to the U.S. Environmental Protection Agency, methanol is less volatile than gasoline, and when it is blended with gasoline, methanol lowers carbon monoxide emissions but increases hydrocarbon emissions. When it is used on its own, methanol causes less ground-level ozone to form than gasoline does. Methanol is not commonly used; estimates in 2001 placed the number of methanol vehicles at 1,000 or fewer, according to the EPA.