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.
| CAS Number | Chemical Name |
|---|---|
| 75070 | Acetaldehyde |
| 60355 | Acetamide |
| 75058 | Acetonitrile |
| 98862 | Acetophenone |
| 53963 | 2-Acetylaminofluorene |
| 107028 | Acrolein |
| 79061 | Acrylamide |
| 79107 | Acrylic acid |
| 107131 | Acrylonitrile |
| 107051 | Allyl chloride |
| 92671 | 4-Aminobiphenyl |
| 62533 | Aniline |
| 90040 | o-Anisidine |
| 1332214 | Asbestos |
| 71432 | Benzene (including benzene from gasoline) |
| 92875 | Benzidine |
| 98077 | Benzotrichloride |
| 100447 | Benzyl chloride |
| 92524 | Biphenyl |
| 117817 | Bis(2-ethylhexyl)phthalate (DEHP) |
| 542881 | Bis(chloromethyl)ether |
| 75252 | Bromoform |
| 106945 | 1-Bromopropane (See Modification) |
| 106990 | 1,3-Butadiene |
| 156627 | Calcium cyanamide |
| 105602 | Caprolactam (See Modification) |
| 133062 | Captan |
| 63252 | Carbaryl |
| 75150 | Carbon disulfide |
| 56235 | Carbon tetrachloride |
| 463581 | Carbonyl sulfide |
| 120809 | Catechol |
| 133904 | Chloramben |
| 57749 | Chlordane |
| 7782505 | Chlorine |
| 79118 | Chloroacetic acid |
| 532274 | 2-Chloroacetophenone |
| 108907 | Chlorobenzene |
| 510156 | Chlorobenzilate |
| 67663 | Chloroform |
| 107302 | Chloromethyl methyl ether |
| 126998 | Chloroprene |
| 1319773 | Cresols/Cresylic acid (isomers and mixture) |
| 95487 | o-Cresol |
| 108394 | m-Cresol |
| 106445 | p-Cresol |
| 98828 | Cumene |
| 94757 | 2,4-D, salts and esters |
| 3547044 | DDE |
| 334883 | Diazomethane |
| 132649 | Dibenzofurans |
| 96128 | 1,2-Dibromo-3-chloropropane |
| 84742 | Dibutylphthalate |
| 106467 | 1,4-Dichlorobenzene(p) |
| 91941 | 3,3-Dichlorobenzidene |
| 111444 | Dichloroethyl ether (Bis(2-chloroethyl)ether) |
| 542756 | 1,3-Dichloropropene |
| 62737 | Dichlorvos |
| 111422 | Diethanolamine |
| 121697 | N,N-Dimethylaniline |
| 64675 | Diethyl sulfate |
| 119904 | 3,3-Dimethoxybenzidine |
| 60117 | Dimethyl aminoazobenzene |
| 119937 | 3,3'-Dimethyl benzidine |
| 79447 | Dimethyl carbamoyl chloride |
| 68122 | Dimethyl formamide |
| 57147 | 1,1-Dimethyl hydrazine |
| 131113 | Dimethyl phthalate |
| 77781 | Dimethyl sulfate |
| 534521 | 4,6-Dinitro-o-cresol, and salts |
| 51285 | 2,4-Dinitrophenol |
| 121142 | 2,4-Dinitrotoluene |
| 123911 | 1,4-Dioxane (1,4-Diethyleneoxide) |
| 122667 | 1,2-Diphenylhydrazine |
| 106898 | Epichlorohydrin (l-Chloro-2,3-epoxypropane) |
| 106887 | 1,2-Epoxybutane |
| 140885 | Ethyl acrylate |
| 100414 | Ethyl benzene |
| 51796 | Ethyl carbamate (Urethane) |
| 75003 | Ethyl chloride (Chloroethane) |
| 106934 | Ethylene dibromide (Dibromoethane) |
| 107062 | Ethylene dichloride (1,2-Dichloroethane) |
| 107211 | Ethylene glycol |
| 151564 | Ethylene imine (Aziridine) |
| 75218 | Ethylene oxide |
| 96457 | Ethylene thiourea |
| 75343 | Ethylidene dichloride (1,1-Dichloroethane) |
| 50000 | Formaldehyde |
| 76448 | Heptachlor |
| 118741 | Hexachlorobenzene |
| 87683 | Hexachlorobutadiene |
| 77474 | Hexachlorocyclopentadiene |
| 67721 | Hexachloroethane |
| 822060 | Hexamethylene-1,6-diisocyanate |
| 680319 | Hexamethylphosphoramide |
| 110543 | Hexane |
| 302012 | Hydrazine |
| 7647010 | Hydrochloric acid |
| 7664393 | Hydrogen fluoride (Hydrofluoric acid) |
| 7783064 | Hydrogen sulfide (See Modification) |
| 123319 | Hydroquinone |
| 78591 | Isophorone |
| 58899 | Lindane (all isomers) |
| 108316 | Maleic anhydride |
| 67561 | Methanol |
| 72435 | Methoxychlor |
| 74839 | Methyl bromide (Bromomethane) |
| 74873 | Methyl chloride (Chloromethane) |
| 71556 | Methyl chloroform (1,1,1-Trichloroethane) |
| 78933 | Methyl ethyl ketone (2-Butanone) (See Modification) |
| 60344 | Methyl hydrazine |
| 74884 | Methyl iodide (Iodomethane) |
| 108101 | Methyl isobutyl ketone (Hexone) |
| 624839 | Methyl isocyanate |
| 80626 | Methyl methacrylate |
| 1634044 | Methyl tert butyl ether |
| 101144 | 4,4-Methylene bis(2-chloroaniline) |
| 75092 | Methylene chloride (Dichloromethane) |
| 101688 | Methylene diphenyl diisocyanate (MDI) |
| 101779 | 4,4'-Methylenedianiline |
| 91203 | Naphthalene |
| 98953 | Nitrobenzene |
| 92933 | 4-Nitrobiphenyl |
| 100027 | 4-Nitrophenol |
| 79469 | 2-Nitropropane |
| 684935 | N-Nitroso-N-methylurea |
| 62759 | N-Nitrosodimethylamine |
| 59892 | N-Nitrosomorpholine |
| 56382 | Parathion |
| 82688 | Pentachloronitrobenzene (Quintobenzene) |
| 87865 | Pentachlorophenol |
| 108952 | Phenol |
| 106503 | p-Phenylenediamine |
| 75445 | Phosgene |
| 7803512 | Phosphine |
| 7723140 | Phosphorus |
| 85449 | Phthalic anhydride |
| 1336363 | Polychlorinated biphenyls (Aroclors) |
| 1120714 | 1,3-Propane sultone |
| 57578 | beta-Propiolactone |
| 123386 | Propionaldehyde |
| 114261 | Propoxur (Baygon) |
| 78875 | Propylene dichloride (1,2-Dichloropropane) |
| 75569 | Propylene oxide |
| 75558 | 1,2-Propylenimine (2-Methyl aziridine) |
| 91225 | Quinoline |
| 106514 | Quinone |
| 100425 | Styrene |
| 96093 | Styrene oxide |
| 1746016 | 2,3,7,8-Tetrachlorodibenzo-p-dioxin |
| 79345 | 1,1,2,2-Tetrachloroethane |
| 127184 | Tetrachloroethylene (Perchloroethylene) |
| 7550450 | Titanium tetrachloride |
| 108883 | Toluene |
| 95807 | 2,4-Toluene diamine |
| 584849 | 2,4-Toluene diisocyanate |
| 95534 | o-Toluidine |
| 8001352 | Toxaphene (chlorinated camphene) |
| 120821 | 1,2,4-Trichlorobenzene |
| 79005 | 1,1,2-Trichloroethane |
| 79016 | Trichloroethylene |
| 95954 | 2,4,5-Trichlorophenol |
| 88062 | 2,4,6-Trichlorophenol |
| 121448 | Triethylamine |
| 1582098 | Trifluralin |
| 540841 | 2,2,4-Trimethylpentane |
| 108054 | Vinyl acetate |
| 593602 | Vinyl bromide |
| 75014 | Vinyl chloride |
| 75354 | Vinylidene chloride (1,1-Dichloroethylene) |
| 1330207 | Xylenes (isomers and mixture) |
| 95476 | o-Xylenes |
| 108383 | m-Xylenes |
| 106423 | p-Xylenes |
| 0 | Antimony Compounds |
| 0 | Arsenic Compounds (inorganic including arsine) |
| 0 | Beryllium Compounds |
| 0 | Cadmium Compounds |
| 0 | Chromium Compounds |
| 0 | Cobalt Compounds |
| 0 | Coke Oven Emissions |
| 0 | Cyanide Compounds 1 |
| 0 | Glycol ethers 2 (See Modification) |
| 0 | Lead Compounds |
| 0 | Manganese Compounds |
| 0 | Mercury Compounds |
| 0 | Fine mineral fibers 3 |
| 0 | Nickel Compounds |
| 0 | Polycyclic Organic Matter 4 |
| 0 | Radionuclides (including radon) 5 |
| 0 | Selenium Compounds |
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.
Modifications
Pollutants removed from the list of hazardous air pollutants:
Methyl Ethyl Ketone – removed from the list of hazardous air pollutants in December 2005 - Federal Register - December 19, 2005 (70 FR 75047).
Ethylene glycol monobutyl ether (EGBE) (2-Butoxyethanol) - removed from the list of hazardous air pollutants (glycol ethers category) in November 2004 - Federal Register - November 29, 2004 (69 FR 69320).
Caprolactam – removed from the list of hazardous air pollutants in June 1996 - Federal Register - June 18, 1996 (61 FR 30816).
Hydrogen Sulfide – added to the list inadvertently but removed by Congress with Presidential approval in 1991.
Surfactant alcohol ethoxylates and their derivatives - removed from the list of hazardous air pollutants in August 2000 - Federal Register – August 2, 2000 (65 FR 47342). To implement this action, EPA revised footnote 2 of the list (42 U.S.C. 7412(b)(1)) to read as follows:
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 C7 or less; or R = phenyl or alkyl substituted phenyl;
R' = H or alkyl C7 or less; or OR’ consisting of carboxylic acid ester, sulfate, phosphate, nitrate, or sulfonate.
Pollutants added to the list of hazardous air pollutants:
1-bromopropane – On January 5, 2022, EPA issued a final rule to add 1-bromopropane (1-BP) to the Clean Air Act's list of hazardous air pollutants. Learn more.