Hazardous Air Pollutants and Toxic Air Pollutants (HAPs and TAPs)
The Clean Air Act, amended by Congress in 1990, identified 189 Hazardous Air Pollutants, or HAPs, for regulation. HAPs are pollutants "known to cause or may reasonably be anticipated to cause adverse effects to human health or adverse environmental effects" [Section 112 (b)]. They may be emitted from stationary sources (industrial processes) or mobile sources (cars, trucks and other vehicles).
Federal HAPs are regulated by specified controls known as maximum achievable control technology standards (MACTs) and generally achievable control technology standards (GACTs). These standards apply to area and industrial source categories, such as paper mills and fuel combustion sources. There are currently 187 federal HAPs, following the delisting of caprolactam in 1996 and methyl ethyl ketone in 2005.
North Carolina has a health-based control program that regulates 97 Toxic Air Pollutants or TAPs. There are overlaps between the HAPs and TAPs lists. The North Carolina Air Toxics program focuses on chemicals emitted by stationary sources. Modeled ambient levels of TAPs at the source property boundary must not exceed established health-based acceptable ambient levels (AALs). AALs are recommended by the Secretary's Science Advisory Board (NCSAB) and approved by the North Carolina Environmental Commission (EMC).
The Rules containing AALs and permitting procedures for North Carolina TAPs are found in:
North Carolina can also require additional facility emission limits beyond those specified by applicable federal MACTs to ensure that AALs are not exceeded.
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