POLLUTION LOCATOR|Changes in Emissions Since 1996 Could Affect the Validity of Concentration Estimates

EPA's National-Scale Air Toxics Assessment is based on 1996 emissions data, and important changes in pollution sources may have occurred since that time in response to regulatory controls and a variety of economic factors. Significant air toxics reductions are resulting from the implementation of Federal and State programs or from industry initiatives. Increases in pollution are also occuring in some areas as a result of economic activity.

One of the goals of the 1990 Clean Air Act Amendments was to compensate for the previous, very slow process of controlling emissions of hazardous air pollutants (HAPs). Prior to 1990, EPA had taken twenty years to issue emissions standards for only seven HAPs (asbestos, benzene, beryllium, arsenic, mercury, radionuclides and vinyl chloride). Those standards reduced HAP emissions by only 125,000 tons. The 1990 Amendments gave EPA a fixed timeline for issuing rules to reduce emissions of 188 HAPs from major sources. In addition to establishing that lifetime cancer risks from major sources should not exceed one in a million, the 1990 Amendments contain several other requirements for regulating hazardous air pollutants.

The 1990 Amendments adopt a "technology first" approach to reducing HAP emissions from major industrial facilities. Maximum Achievable Control Technology standards are being promulgated which require facilities to reduce their emissions to levels achieved by the best performing facilities within the same source category. To date, EPA has issued 44 standards covering some of the 170 categories of major industrial sources, including chemical plants, oil refineries, aerospace manufacturers and steel mills, as well as eight categories of smaller sources, such as dry cleaners commercial sterilizers, smelters and electroplating facilities. These rules have been slowly coming into force over the last five years. Additional rules governing more categories have been proposed but are not yet in effect. EPA estimates that these standards will reduce emissions of hazardous air pollutants significantly when fully implemented.

For mobile sources, the Clean Air Act requires that EPA establish "reasonable requirements to control hazardous air pollutants from motor vehicles and motor vehicle fuels." Hazardous air pollutant emissions from cars have steadily declined due to tailpipe and evaporative emission standards, federal testing procedures, the National Low Emission Vehicle program and regulations regarding the introduction of reformulated gasoline and alternative fuels. However, the improvements from better emissions controls for cars have been eroded by the fact that people are driving more miles each year, and that the number of cars in urban areas keeps going up.

Small business sources have been subjected to substantially less regulatory control than point sources or mobile sources, and their contribution to toxic air pollution is increasing. The 1990 Amendments also require EPA to develop an urban air toxics strategy focused on area sources emitting the most toxic HAPs, with the goal of reducing overall cancer risks from hazardous air pollutants by 75%. EPA has issued its Urban Air Toxics Strategy, and is focusing new regulatory attention on area source categories like dry cleaning operations, industrial boilers, hospitals and sewage treatment plants.

Some states with strong air toxics regulatory programs have imposed additional controls on pollution sources, which are also generating substantial emissions reductions. For example, the California Air Resources Board and a number of regional Air Quality Management Districts have acted to reduce emissions of hazardous air pollutants. California has adopted more stringent automobile emissions standards than EPA's national standards, creating markets for very low emissions and zero emission vehicles. Since 1996, state regulations have required the use of cleaner-burning, low-sulfur gasoline which has substantially reduced benzene emissions from automobiles. The Air Resources Board has also promulgated more stringent emissions standards for light trucks and diesel-powered vehicles, further reducing emissions of hazardous air pollutants in California.