- National Emissions Standards for Hazardous Air Pollutants
The National Emissions Standards for Hazardous Air Pollutants (NESHAPs) are emissions standards set by the United States EPA for an air pollutant not covered by NAAQS that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness. The standards for a particular source category require the maximum degree of emission reduction that the EPA determines to be achievable, which is known as the Maximum Achievable Control Technology (MACT) . These standards are authorized by Section 112 of the Clean Air Act and the regulations are published in 40 CFR Parts 61 and 63.
The USEPA regulates the following hazardous air pollutants via the MACT standards:
CAS Number Chemical Name Notes 75-07-0 Acetaldehyde 60-35-5 Acetamide 75-05-8 Acetonitrile 98-86-2 Acetophenone (Methyl Phenyl Ketone) 53-96-3 2-Acetylaminofluorene 107-02-8 Acrolein 79-06-1 Acrylamide 79-10-7 Acrylic acid 107-13-1 Acrylonitrile 107-05-1 Allyl chloride (3-Chloropropene) 92-67-1 4-Aminobiphenyl 62-53-3 Aniline 90-04-0 o-Anisidine 1332-21-4 Asbestos 71-43-2 Benzene including benzene from gasoline 92-87-5 Benzidine 98-07-7 Benzotrichloride 100-44-7 Benzyl chloride 92-52-4 Biphenyl 117-81-7 Bis(2-ethylhexyl)phthalate (DEHP) 542-88-1 Bis(chloromethyl)ether 75-25-2 Bromoform (Tribromomethane) 106-99-0 1,3-Butadiene 156-62-7 Calcium cyanamide 105-60-2 Caprolactam delisted on June 18, 1996 133-06-2 Captan 63-25-2 Carbaryl 75-15-0 Carbon disulfide 56-23-5 Carbon tetrachloride (Tetrachloromethane) 463-58-1 Carbonyl sulfide 120-80-9 Catechol 133-90-4 Chloramben 57-74-9 Chlordane 7782-50-5 Chlorine 79-11-8 Chloroacetic acid 532-27-4 2-Chloroacetophenone 108-90-7 Chlorobenzene 510-15-6 Chlorobenzilate 67-66-3 Chloroform (Trichloromethane) 107-30-2 Chloromethyl methyl ether 126-99-8 Chloroprene 1319-77-3 Cresols/Cresylic acid (isomers and mixture) 95-48-7 o-Cresol 108-39-4 m-Cresol 106-44-5 p-Cresol 98-82-8 Cumene 94-75-7 2,4-D, salts and esters 3547-04-4 Dichlorodiphenyldichloroethylene (DDE) 334-88-3 Diazomethane 132-64-9 Dibenzofurans 96-12-8 1,2-Dibromo-3-chloropropane (DBCP) 84-74-2 Dibutylphthalate 106-46-7 1,4-Dichlorobenzene (p-Dichlorobenzene) 91-94-1 3,3'-Dichlorobenzidine 111-44-4 Dichloroethyl ether (Bis(2-chloroethyl)ether) 542-75-6 1,3-Dichloropropene 62-73-7 Dichlorvos 111-42-2 Diethanolamine 64-67-5 Diethyl sulfate 119-90-4 3,3'-Dimethoxybenzidine 60-11-7 Dimethyl aminoazobenzene 119-93-7 3,3'-Dimethyl benzidine 79-44-7 Dimethyl carbamoyl chloride 68-12-2 Dimethyl formamide 57-14-7 1,1-Dimethyl hydrazine 131-11-3 Dimethyl phthalate 77-78-1 Dimethyl sulfate 121-69-7 N,N-Dimethylaniline Clean Air Act erroneously lists N,N-Diethylaniline 534-52-1 4,6-Dinitro-o-cresol, and salts 51-28-5 2,4-Dinitrophenol 121-14-2 2,4-Dinitrotoluene 123-91-1 1,4-Dioxane (1,4-Diethyleneoxide) 122-66-7 1,2-Diphenylhydrazine 106-89-8 Epichlorohydrin (l-Chloro-2,3-epoxypropane) 106-88-7 1,2-Epoxybutane 140-88-5 Ethyl acrylate 100-41-4 Ethyl benzene 51-79-6 Ethyl carbamate (Urethane) 75-00-3 Ethyl chloride (Chloroethane) 106-93-4 Ethylene dibromide (1,2-Dibromoethane) 107-06-2 Ethylene dichloride (1,2-Dichloroethane) 107-21-1 Ethylene glycol 151-56-4 Ethylene imine (Aziridine) 75-21-8 Ethylene oxide 96-45-7 Ethylene thiourea 75-34-3 Ethylidene dichloride (1,1-Dichloroethane) 50-00-0 Formaldehyde 76-44-8 Heptachlor 118-74-1 Hexachlorobenzene 87-68-3 Hexachlorobutadiene 77-47-4 Hexachlorocyclopentadiene 67-72-1 Hexachloroethane 822-06-0 Hexamethylene-1,6-diisocyanate 680-31-9 Hexamethylphosphoramide 110-54-3 Hexane 302-01-2 Hydrazine 7647-01-0 Hydrochloric acid 7664-39-3 Hydrogen fluoride (Hydrofluoric acid) 7783-06-4 Hydrogen sulfide delisted on December 4, 1991 123-31-9 Hydroquinone 78-59-1 Isophorone 58-89-9 Lindane (all isomers) 108-31-6 Maleic anhydride 67-56-1 Methanol 72-43-5 Methoxychlor 74-83-9 Methyl bromide (Bromomethane) 74-87-3 Methyl chloride (Chloromethane) 71-55-6 Methyl chloroform (1,1,1-Trichloroethane) 78-93-3 Methyl ethyl ketone (2-Butanone or MEK) delisted on December 19, 2005 60-34-4 Methyl hydrazine 74-88-4 Methyl iodide (Iodomethane) 108-10-1 Methyl isobutyl ketone (Hexone or MIBK) currently under review for delisting 624-83-9 Methyl isocyanate 80-62-6 Methyl methacrylate 1634-04-4 Methyl tert-butyl ether 101-14-4 4,4'-Methylene bis(2-chloroaniline) 75-09-2 Methylene chloride (Dichloromethane) 101-68-8 Methylene diphenyl diisocyanate (MDI) currently under review for delisting 101-77-9 4,4'-Methylenedianiline 91-20-3 Naphthalene 98-95-3 Nitrobenzene 92-93-3 4-Nitrobiphenyl 100-02-7 4-Nitrophenol 79-46-9 2-Nitropropane 684-93-5 N-Nitroso-N-methylurea 62-75-9 N-Nitrosodimethylamine 59-89-2 N-Nitrosomorpholine 56-38-2 Parathion 82-68-8 Pentachloronitrobenzene (Quintobenzene) 87-86-5 Pentachlorophenol 108-95-2 Phenol 106-50-3 p-Phenylenediamine 75-44-5 Phosgene 7803-51-2 Phosphine 7723-14-0 Phosphorus 85-44-9 Phthalic anhydride 1336-36-3 Polychlorinated biphenyls (Aroclors) 1120-71-4 1,3-Propane sultone 57-57-8 beta-Propiolactone 123-38-6 Propionaldehyde 114-26-1 Propoxur (Baygon) 78-87-5 Propylene dichloride (1,2-Dichloropropane) 75-56-9 Propylene oxide 75-55-8 1,2-Propylenimine (2-Methyl aziridine) 91-22-5 Quinoline 106-51-4 Quinone 100-42-5 Styrene 96-09-3 Styrene oxide 1746-01-6 2,3,7,8-Tetrachlorodibenzo-p-dioxin 79-34-5 1,1,2,2-Tetrachloroethane 127-18-4 Tetrachloroethylene (Perchloroethylene) 7550-45-0 Titanium tetrachloride 108-88-3 Toluene 95-80-7 2,4-Toluene diamine 584-84-9 2,4-Toluene diisocyanate 95-53-4 o-Toluidine 8001-35-2 Toxaphene (chlorinated camphene) 120-82-1 1,2,4-Trichlorobenzene 79-00-5 1,1,2-Trichloroethane 79-01-6 Trichloroethylene 95-95-4 2,4,5-Trichlorophenol 88-06-2 2,4,6-Trichlorophenol 121-44-8 Triethylamine 1582-09-8 Trifluralin 540-84-1 2,2,4-Trimethylpentane 108-05-4 Vinyl acetate 593-60-2 Vinyl bromide (Bromoethene) 75-01-4 Vinyl chloride (Chloroethene) 75-35-4 Vinylidene chloride (1,1-Dichloroethylene) 1330-20-7 Xylenes (isomers and mixture) 95-47-6 o-Xylenes 108-38-3 m-Xylenes 106-42-3 p-Xylenes n/a Antimony Compounds n/a Arsenic Compounds inorganic including arsine n/a Beryllium Compounds n/a Cadmium Compounds n/a Chromium Compounds n/a Cobalt Compounds n/a Coke Oven Emissions n/a Cyanide Compounds1 n/a Glycol ethers2 n/a Lead Compounds n/a Manganese Compounds n/a Mercury Compounds n/a Fine mineral fibers3 n/a Nickel Compounds n/a Polycylic Organic Matter4 n/a Radionuclides5 including radon n/a Selenium Compounds
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 C7 (chain of 7 carbon atoms) or less; or phenyl or alkyl substituted phenyl
- R' = H or alkyl C7 or less; or OR' consisting of carboxylic acid ester, sulfate, phosphate, nitrate, or sulfonate. Polymers are excluded from the glycol category, as well as surfactant alcohol ethoxylates (where R is an alkyl C8 or greater) and their derivatives, and ethylene glycol monobutyl ether (CAS 111-76-2).
- ^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 °C.
- ^5 A type of atom which spontaneously undergoes radioactive decay.
Most 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:
"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. These sources may release air toxics from equipment leaks, when materials are transferred from one location to another, or during discharge through emission stacks or vents
"Area" sources consist of smaller-size facilities that release lesser quantities 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 combination of air toxics. Though emissions from individual area sources are often relatively small, collectively their emissions can be of concern - particularly where large numbers of sources are located in heavily populated areas.
The United States 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). 
- Air pollution in the United States
- Overview, a brief description of the sections of the Clean Air Act related to air toxics as well as further links to relevant rules, reports, and programs.
- Specific MACT regulation summaries
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