Pollutants & Sources
The PollutantsHazardous air pollutants, also known as toxic air pollutants or air toxics, are those pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects. EPA is required to control 188 hazardous air pollutants. Examples of toxic air pollutants include benzene, which is found in gasoline; perchlorethlyene, which is emitted from some dry cleaning facilities; and methylene chloride, which is used as a solvent and paint stripper by a number of industries. Through appropriate rulemaking, the Clean Air Act list can be modified. A current list of modifications is available. Some clarification on certain pollutant aggregation is also available.
The SourcesMost air toxics originate from human-made sources,
including mobile
sources (e.g., cars, trucks, buses) and stationary sources (e.g.,
factories, refineries, power plants), as well as indoor
sources (e.g., building materials and activities such as cleaning).
There are two types of stationary sources that generate routine
emissions of air toxics:
EPA published the initial list of "source categories" in 1992 (57FR31576 , July 16, 1992) and since that time has issued several revisions and updates to the list and promulgation schedule. For each listed source category, EPA indicates whether the sources are considered to be "major" sources or "area" sources. The 1990 Clean Air Act Amendments direct EPA to set standards for all major sources of air toxics (and some area sources that are of particular concern). |