POLLUTION LOCATOR|Regulatory Coverage: Clean Air Act Hazardous Air Pollutants

The federal Clean Air Act, as amended in 1990, set out a list of 189 hazardous air pollutants (HAPs). These are only some of the toxic chemicals being released to air, but many more than the Clean Air Act had been able to address prior to 1990. EPA was instructed to set "national emissions standards for hazardous air pollutants" (NESHAPs) specifically for the 189 HAPs. (The 1990 amendment reflected Congress's frustration with the fact that, in the two decades prior to 1990, standards for only a half-dozen HAPs had been set.) NESHAPs, however, do not define the maximum allowable concentration of a HAP in outdoor air. Instead, they are based on EPA's determination of the "maximum achievable control technology" in an industry. EPA surveys the pollutant releases from an industry, identifies the firms that are doing the best job of controlling those releases, and then sets so-called "performance standards" for that industry, in the form of NESHAPs that usually define the rate at which pollutants can be released. Instead of setting specific limits for each HAP that an industry releases, a NESHAP focuses only on a few priority chemicals, assuming that control of the few priority chemicals will succeed in controlling other hazardous air pollutants coming out of the same source. Because they are based on performance capability, NESHAPs can be different for different industries, even if the chemicals involved are the same.

Eventually, after setting NESHAPs, EPA is supposed to go back and see whether compliance with each NESHAP is in fact protecting public health with "an ample margin of safety." If not, EPA is then supposed to set additional standards for different categories of industrial emissions, this time based on health protection rather than on available technology.

See a list of the Hazardous Air Pollutants (HAPs)

More information about NESHAPs and the regulation of Hazardous Air Pollutants (HAPs):


More information about the Clean Air Act: