The National Emission Standards for Hazardous Air Pollutants (NESHAP) are air pollution standards issued by the United States Environmental Protection Agency (EPA). The standards, authorized by the Clean Air Act, are for pollutants not covered by the National Ambient Air Quality Standards (NAAQS) that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness.[1]

Maximum Achievable Control Technology standards

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) standards.[2] These standards are authorized by Section 112 of the 1970 Clean Air Act and the regulations are published in the Code of Federal Regulations (CFR).[3]

Pollutants

EPA regulates the following hazardous air pollutants with the MACT standards.

CAS NumberChemical NameNotes
75-07-0Acetaldehyde
60-35-5Acetamide
75-05-8Acetonitrile
98-86-2Acetophenone (Methyl Phenyl Ketone)
53-96-32-Acetylaminofluorene
107-02-8Acrolein
79-06-1Acrylamide
79-10-7Acrylic acid
107-13-1Acrylonitrile
107-05-1Allyl chloride (3-Chloropropene)
92-67-14-Aminobiphenyl
62-53-3Aniline
90-04-0o-Anisidine
1332-21-4Asbestos
71-43-2Benzeneincluding benzene from gasoline
92-87-5Benzidine
98-07-7Benzotrichloride
100-44-7Benzyl chloride
92-52-4Biphenyl
117-81-7Bis(2-ethylhexyl)phthalate (DEHP)
542-88-1Bis(chloromethyl)ether
75-25-2Bromoform (Tribromomethane)
106-99-01,3-Butadiene
156-62-7Calcium cyanamide
105-60-2CaprolactamDelisted on June 18, 1996
133-06-2Captan
63-25-2Carbaryl
75-15-0Carbon disulfide
56-23-5Carbon tetrachloride (Tetrachloromethane)
463-58-1Carbonyl sulfide
120-80-9Catechol
133-90-4Chloramben
57-74-9Chlordane
7782-50-5Chlorine
79-11-8Chloroacetic acid
532-27-42-Chloroacetophenone
108-90-7Chlorobenzene
510-15-6Chlorobenzilate
67-66-3Chloroform (Trichloromethane)
107-30-2Chloromethyl methyl ether
126-99-8Chloroprene
1319-77-3Cresols/Cresylic acid (isomers and mixture)
95-48-7o-Cresol
108-39-4m-Cresol
106-44-5p-Cresol
98-82-8Cumene
94-75-72,4-D, salts and esters
3547-04-4Dichlorodiphenyldichloroethylene (DDE)
334-88-3Diazomethane
132-64-9Dibenzofurans
96-12-81,2-Dibromo-3-chloropropane (DBCP)
84-74-2Dibutylphthalate
106-46-71,4-Dichlorobenzene (p-Dichlorobenzene)
91-94-13,3'-Dichlorobenzidine
111-44-4Dichloroethyl ether (Bis(2-chloroethyl)ether)
542-75-61,3-Dichloropropene
62-73-7Dichlorvos
111-42-2Diethanolamine
64-67-5Diethyl sulfate
119-90-43,3'-Dimethoxybenzidine
60-11-7Dimethyl aminoazobenzene
119-93-73,3'-Dimethyl benzidine
79-44-7Dimethylcarbamoyl chloride
68-12-2Dimethyl formamide
57-14-71,1-Dimethyl hydrazine
131-11-3Dimethyl phthalate
77-78-1Dimethyl sulfate
121-69-7N,N-DimethylanilineClean Air Act erroneously lists N,N-Diethylaniline
534-52-14,6-Dinitro-o-cresol, and salts
51-28-52,4-Dinitrophenol
121-14-22,4-Dinitrotoluene
123-91-11,4-Dioxane (1,4-Diethyleneoxide)
122-66-71,2-Diphenylhydrazine
106-89-8Epichlorohydrin (l-Chloro-2,3-epoxypropane)
106-88-71,2-Epoxybutane
140-88-5Ethyl acrylate
100-41-4Ethyl benzene
51-79-6Ethyl carbamate (Urethane)
75-00-3Ethyl chloride (Chloroethane)
106-93-4Ethylene dibromide (1,2-Dibromoethane)
107-06-2Ethylene dichloride (1,2-Dichloroethane)
107-21-1Ethylene glycol
151-56-4Ethylene imine (Aziridine)
75-21-8Ethylene oxide
96-45-7Ethylene thiourea
75-34-3Ethylidene dichloride (1,1-Dichloroethane)
50-00-0Formaldehyde
76-44-8Heptachlor
118-74-1Hexachlorobenzene
87-68-3Hexachlorobutadiene
77-47-4Hexachlorocyclopentadiene
67-72-1Hexachloroethane
822-06-0Hexamethylene-1,6-diisocyanate
680-31-9Hexamethylphosphoramide
110-54-3Hexane
302-01-2Hydrazine
7647-01-0Hydrochloric acid
7664-39-3Hydrogen fluoride (Hydrofluoric acid)
7783-06-4Hydrogen sulfideDelisted on December 4, 1991
123-31-9Hydroquinone
78-59-1Isophorone
58-89-9Lindane (all isomers)
108-31-6Maleic anhydride
67-56-1Methanol
72-43-5Methoxychlor
74-83-9Methyl bromide (Bromomethane)
74-87-3Methyl chloride (Chloromethane)
71-55-6Methyl chloroform (1,1,1-Trichloroethane)
78-93-3Methyl ethyl ketone (2-Butanone or MEK)Delisted on December 19, 2005
60-34-4Methyl hydrazine
74-88-4Methyl iodide (Iodomethane)
108-10-1Methyl isobutyl ketone (Hexone or MIBK)currently under review for delisting
624-83-9Methyl isocyanate
80-62-6Methyl methacrylate
1634-04-4Methyl tert-butyl ether
101-14-44,4'-Methylene bis(2-chloroaniline)
75-09-2Methylene chloride (Dichloromethane)
101-68-8Methylene diphenyl diisocyanate (MDI)currently under review for delisting
101-77-94,4'-Methylenedianiline
91-20-3Naphthalene
98-95-3Nitrobenzene
92-93-34-Nitrobiphenyl
100-02-74-Nitrophenol
79-46-92-Nitropropane
684-93-5N-Nitroso-N-methylurea
62-75-9N-Nitrosodimethylamine
59-89-2N-Nitrosomorpholine
56-38-2Parathion
82-68-8Pentachloronitrobenzene (Quintobenzene)
87-86-5Pentachlorophenol
108-95-2Phenol
106-50-3p-Phenylenediamine
75-44-5Phosgene
7803-51-2Phosphine
7723-14-0Phosphorus
85-44-9Phthalic anhydride
1336-36-3Polychlorinated biphenyls (Aroclors)
1120-71-41,3-Propane sultone
57-57-8beta-Propiolactone
123-38-6Propionaldehyde
114-26-1Propoxur (Baygon)
78-87-5Propylene dichloride (1,2-Dichloropropane)
75-56-9Propylene oxide
75-55-81,2-Propylenimine (2-Methyl aziridine)
91-22-5Quinoline
106-51-4Quinone
100-42-5Styrene
96-09-3Styrene oxide
1746-01-62,3,7,8-Tetrachlorodibenzo-p-dioxin
79-34-51,1,2,2-Tetrachloroethane
127-18-4Tetrachloroethylene (Perchloroethylene)
7550-45-0Titanium tetrachloride
108-88-3Toluene
95-80-72,4-Toluene diamine
584-84-92,4-Toluene diisocyanate
95-53-4o-Toluidine
8001-35-2Toxaphene (chlorinated camphene)
120-82-11,2,4-Trichlorobenzene
79-00-51,1,2-Trichloroethane
79-01-6Trichloroethylene
95-95-42,4,5-Trichlorophenol
88-06-22,4,6-Trichlorophenol
121-44-8Triethylamine
1582-09-8Trifluralin
540-84-12,2,4-Trimethylpentane
108-05-4Vinyl acetate
593-60-2Vinyl bromide (Bromoethene)
75-01-4Vinyl chloride (Chloroethene)
75-35-4Vinylidene chloride (1,1-Dichloroethylene)
1330-20-7Xylenes (isomers and mixture)
95-47-6o-Xylenes
108-38-3m-Xylenes
106-42-3p-Xylenes
n/aAntimony Compounds
n/aArsenic Compoundsinorganic including arsine
n/aBeryllium Compounds
n/aCadmium Compounds
n/aChromium Compounds
n/aCobalt Compounds
n/aCoke Oven Emissions
n/aCyanide Compounds1
n/aGlycol ethers2
n/aLead Compounds
n/aManganese Compounds
n/aMercury Compounds
n/aFine mineral fibers3
n/aNickel Compounds
n/aPolycylic Organic Matter4
n/aRadionuclides5including radon
n/aSelenium 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.[4]

Pollution sources

Most air toxics originate from human-made sources, including mobile sources (e.g., cars, trucks, buses) and stationary sources (e.g., factories, oil 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:

  1. Major sources are defined as sources that emit 10 or more tons per year of any of the listed toxic air pollutants, or 25 or more tons per year of a mixture of air toxics. These sources may release air toxics from fugitive emissions (equipment leaks), when materials are transferred from one location to another, or during discharge through emission stacks or vents.
  2. Area sources consist of smaller facilities that release lesser quantities of toxic pollutants into the air. Area sources are defined as sources that do not emit more than 10 tons per year of a single air toxic or more than 25 tons per year of a combination of air toxics. Although the 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.

EPA published its initial list of source categories in 1992.[5] Subsequently the agency issued several revisions and updates to the list and the regulatory 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 for some area sources that are of particular concern. EPA is required to review all source category regulations every eight years.[6]

See also

References

  1. United States. Clean Air Amendments of 1970. Pub. L. 91–604 Section 112. 42 U.S.C. § 7412
  2. "Reducing Emissions of Hazardous Air Pollutants". Washington, D.C.: United States Environmental Protection Agency (EPA). 2021-01-26.
  3. EPA. "National Emission Standards for Hazardous Air Pollutants." Code of Federal Regulations, 40 CFR 61. “National Emission Standards for Hazardous Air Pollutants for Source Categories.” 40 CFR 63
  4. "Initial List of Hazardous Air Pollutants with Modifications". EPA. 2022-01-05.
  5. EPA (1992-07-16). "Initial List of Categories of Sources Under Section 112(c)(1) of the Clean Air Act Amendments of 1990." Federal Register, 57 FR 31576.
  6. "Risk and Technology Review of the National Emissions Standards for Hazardous Air Pollutants". Stationary Sources of Air Pollution. EPA. 2022-02-08.
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