Sources and geographic differences in air releases of benzene in the United States.

The National Emissions Inventory (NEI) presents the most comprehensive outdoor air pollution data available in the US. It includes releases of the criteria air pollutants and volatile organic compounds and distinguishes releases from four different sources: road (vehicles), non-road (farm equipment, lawn mowers, etc.), point (industries, power plants, etc.), and non-point (gas stations, oil, and gas wells, etc.). We show the distribution of releases of benzene by these categories in different states in the U.S. A goal is to determine relative releases from oil and gas extraction as compared to those from vehicles and large point sources. We find that road, non-road, and non-point sources are approximately equal in most states without oil and gas extraction, while point sources are relatively minor contributors. In states with oil and gas extraction, the non-point sources predominate, while in urban areas, on-road sources are dominant. Benzene is a known human carcinogen and has other adverse effects on the hematopoietic, immune, and other systems. These risks are particularly elevated in those individuals working in or living near sites of oil and gas extraction and in urban areas with high vehicle traffic.