epa mact rules

Toxic Air Pollutants for Regulators

Toxic (also called hazardous) air pollutants are those pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or to cause adverse environmental effects. The degree to which a toxic air pollutant affects a person’s health depends on many factors, including the quantity of pollutant the person is exposed to, the duration and frequency of exposures, the toxicity of the chemical, and the person’s state of health and susceptibility.

The 1990 Clean Air Act Amendments list 188 toxic air pollutants that the US EPA is required to control. (The list originally included 189 chemicals. Based on new scientific information, EPA removed caprolactam from the list in 1996; thus, the current list includes 188 pollutants.) Examples of toxic air pollutants include benzene, which is found in gasoline; perchloroethylene, 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. Examples of other listed air toxics include dioxin, asbestos, toluene, and metals such as cadmium, mercury, chromium, and lead compounds.

Routine emissions from stationary sources constitute almost one-half of all manmade air toxics emissions. There are two types of stationary sources that generate routine emissions of air toxics:

• Major sources are defined as sources that emit 10 tons per year of any of the listed toxic air pollutants, or 25 tons per year of a mixture of air toxics.
• Area sources consist of smaller sources, each releasing smaller amounts of toxic pollutants into the air.
• Area sources are defined as sources that emit less than 10 tons per year of a single air toxic, or less than 25 tons per year of a mixture of air toxics.

Source - http://www.epa.gov/oar/oaqps/takingtoxics/p1.html#9

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