Initial List of Hazardous Air Pollutants with Modifications

Under the Clean Air Act, EPA is required to regulate emissions of hazardous air pollutants.  This original list included 189 pollutants.  Since 1990, EPA has modified the list through rulemaking to include 188 hazardous air pollutants.   

NOTE: For all listings above which contain the word "compounds" and for glycol ethers, the following applies: Unless otherwise specified, these listings are defined as including any unique chemical substance that contains the named chemical (i.e., antimony, arsenic, etc.) as part of that chemical's infrastructure.

1 - X'CN where X = H' or any other group where a formal dissociation may occur. For example KCN or Ca(CN)2

2 - Includes mono- and di- ethers of ethylene glycol, diethylene glycol, and triethylene glycol R-(OCH2CH2)n -OR' where
               n = 1, 2, or 3
               R = alkyl or aryl groups
               R' = R, H, or groups which, when removed, yield glycol ethers with the structure: R-(OCH2CH)n-OH. Polymers are excluded from the glycol category. (See Modification)

3 - Includes mineral fiber emissions from facilities manufacturing or processing glass, rock, or slag fibers (or other mineral derived fibers) of average diameter 1 micrometer or less.

4 - Includes organic compounds with more than one benzene ring, and which have a boiling point greater than or equal to 100 ºC.

5 - A type of atom which spontaneously undergoes radioactive decay.