Air toxics are air pollutants that cause adverse health effects. Air Toxics and Public Health Motor vehicles are such an integral part of our society that virtually everyone is exposed to their emissions. Some air toxics, such as benzene, are components of gasoline.
Cars emit benzene as unburned fuel, or as fuel vapors that simply evaporate.
A significant amount of automotive benzene comes from the incomplete combustion of compounds such as toluene and xylene that are chemically very similar to benzene. Like benzene itself, these compounds are added to gasoline to increase octane. Formaldehyde also forms in the atmosphere from certain hydrocarbons in the same chemical reactions that form ozone. This program has contributed to the overall reduction of air toxics emissions seen over the past several years. The control of air toxics emissions from motor vehicles has been addressed at the federal level through technological controls on motor vehicles such as catalytic converters.