Air Toxics

The 1990 Clean Air Act (CAA) required the Environmental Protection Agency (EPA) to regulate the emission of 188 hazardous air pollutants, or HAPs. To accomplish this EPA has develoved 106 technology-based MACT standards, or Maximum Achievable Control Standards, to minimize emissions at stationary and other smaller area sources. These standards can be found in the Code of Federal Regulations at Title 40 (Protection of Environment), Part 63 (Standards Emission Standards for Hazardous Air Pollutants for Stationary Sources). For an electronic compilation of the standards, check out the Government Printing Office's e-CFR Database.

Within 8 years after promulgation of the MACT standards for each category of sources EPA must promulgate additional "residual risk" standards if required to provide an ample margin of safety to protect public health. EPA must also regulate sources that contribute to 90% the area source emissions of the 30 HAPS that present the greatest threat to public health in an urban area.

Prior to 1990, EPA established 23 standards of performance based on the risk of certain hazardous air pollutants. These standards are commonly known as NESHAPs or National Emission Standards for Hazardous Air Pollutants. These standards can be found in the Code of Federal Regulations at Title 40 (Protection of Environment), Part 61 (Standards Emission Standards for Hazardous Air Pollutants for Stationary Sources). For an electronic compilation of the standards, check out the Government Printing Office's e-CFR Database.

Generally, state and local air pollution control agencies are responsible for implementation, compliance assistance, and enforcement of the MACT and NESHAP standards. EPA retains concurrent enforcement authority and is also available to provide technical assistance when a state or local agency seeks help. EPA also retains a few of the MACT and NESHAP responsibilities -- such as the ability to approve alternative monitoring methods -- to maintain a minimum level of national consistency.

If you have questions about the standards, we encourage you to first discuss them with your respective state or local air pollution control agency. If you are located outside of the Region 7 geographic area, which includes Iowa, Kansas, Missouri, and Nebraska, please check with your state or local agency or EPA Regional Office. If you are located in Region 7 and your state or local agency is unable to assist, you may contact us for assistance on the MACT or NESHAP standard of interest.

Air Toxics

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