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 CompoundsNOTE: 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.
