Although section 112 of the 1970 CAA granted the EPA broad authority to adopt stringent emission standards for hazardous air pollutants, as of this writing only seven pollutants are listed as hazardous air pollutants. These pollutants are beryllium, mercury, vinyl chloride, asbestos, benzene, radionuclides, and arsenic. Table 4.2.1 shows the NESHAP. Almost all these standards are technology standards.
A hazardous air pollutant is now defined as "any air pollutant listed pursuant to" section 112(b). In section 112(b), Congress established an initial list of 189 hazardous air pollutants. These listed chemicals are initial candidates for regulation under section 112, and the EPA can add other chemicals to the list.
The control of these substances is to be achieved through the initial promulgation of technology-based emission standards. These standards require major sources to install MACT and area sources to install generally available control technologies (GACT). Major sources are defined as those emitting more than 10 tons per year of any one hazardous air pollutant or more than 25 tons per year of all hazardous air pollutants. MACT/GACT standards
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