Risk and Technology Review of the National Emissions Standards for Hazardous Air Pollutants
The Clean Air Act requires EPA to regulate hazardous air pollutants, also known as air toxics, from categories of industrial facilities in two phases.
- In the first "technology-based" phase, EPA develops standards for controlling the emissions of air toxics from sources in an industry group. These Maximum Achievable Control Technology or MACT standards are based on emissions levels that are already being achieved by the best-controlled and lowest-emitting sources in an industry.
- Within eight years of setting the MACT standards, the Clean Air Act directs EPA to assess the remaining health risks from each source category to determine whether the MACT standards protect public health with an ample margin of safety, and protect against adverse environmental effects. This second phase is a “risk-based” approach called residual risk. Here, the EPA must determine whether more health-protective standards are necessary.
Also, every eight years after setting the MACT standards, the Clean Air Act requires that EPA review and revise the standards, if necessary, to account for improvements in air pollution controls and/or prevention.
- EPA's methodology for conducting risk and technology reviews is described in two documents reviewed by EPA's Science Advisory Board (SAB) :