Regulations last checked for updates: Oct 31, 2025

Title 40 - Protection of Environment last revised: Sep 30, 2029
All TitlesTitle 40Chapter IPart 258Subpart GAppendix Appendix II - Appendix II to Part 258—List of Hazardous Inorganic and Organic Constituents
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Appendix Appendix II - Appendix II to Part 258—List of Hazardous Inorganic and Organic Constituents
Common name 1 CAS RN 2 Chemical abstracts service index name 3
Acenaphthene83-32-9Acenaphthylene, 1,2-dihydro-
Acenaphthylene208-96-8Acenaphthylene
Acetone67-64-12-Propanone
Acetonitrile; Methyl cyanide75-05-8Acetonitrile
Acetophenone98-86-2Ethanone, 1-phenyl-
2-Acetylaminofluorene; 2-AAF53-96-3Acetamide, N-9H-fluoren-2-yl-
Acrolein107-02-82-Propenal
Acrylonitrile107-13-12-Propenenitrile
Aldrin309-00-21,4:5,8-Dimethanonaphthalene, 1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a-hexahydro-(1,4,4a,5,8,8a)-
Allyl chloride107-05-11-Propene, 3-chloro-
4-Aminobiphenyl92-67-1[1,1′-Biphenyl]-4-amine
Anthracene120-12-7Anthracene
Antimony(Total)Antimony
Arsenic(Total)Arsenic
Barium(Total)Barium
Benzene71-43-2Benzene
Benzo[a]anthracene; Benzanthracene56-55-3Benz[a]anthracene
Benzo[b]fluoranthene205-99-2Benz[e]acephenanthrylene
Benzo[k]fluoranthene207-08-9Benzo[k]fluoranthene
Benzo[ghi]perylene191-24-2Benzo[ghi]perylene
Benzo[a]pyrene50-32-8Benzo[a]pyrene
Benzyl alcohol100-51-6Benzenemethanol
Beryllium(Total)Beryllium
alpha-BHC319-84-6Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1α,2α,3β,4α,5β,6β)-
beta-BHC319-85-7Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1α,2β,3α,4β,5α,6β)-
delta-BHC319-86-8Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1α,2α,3α,4β,5α,6β)-
gamma-BHC; Lindane58-89-9Cyclohexane, 1,2,3,4,5,6- hexachloro-,(1α,2α, 3β, 4α,5α,6β)-
Bis(2-chloroethoxy)methane111-91-1Ethane, 1,1′-[methylenebis (oxy)]bis [2-chloro-
Bis(2-chloroethyl)ether; Dichloroethyl ether111-44-4Ethane, 1,1′-oxybis[2-chloro-
Bis(2-chloro-1-methylethyl) ether; 2,2′-Dichlorodiisopropyl ether; DCIP, See footnote 4108-60-1Propane, 2,2′-oxybis[1-chloro-
Bis(2-ethylhexyl) phthalate117-81-71,2-Benzenedicarboxylic acid, bis(2-ethylhexyl)ester
Bromochloromethane; Chlorobromethane74-97-5Methane, bromochloro-
Bromodichloromethane; Dibromochloromethane75-27-4Methane, bromodichloro-
Bromoform; Tribromomethane75-25-2Methane, tribromo-
4-Bromophenyl phenyl ether101-55-3Benzene, 1-bromo-4-phenoxy-
Butyl benzyl phthalate; Benzyl butyl phthalate85-68-71,2-Benzenedicarboxylic acid, butyl phenylmethyl ester
Cadmium(Total)Cadmium
Carbon disulfide75-15-0Carbon disulfide
Carbon tetrachloride56-23-5Methane, tetrachloro-
ChlordaneSee footnote 54,7-Methano-1H-indene, 1,2,4,5,6,7,8,8-octachloro-2,3,3a,4,7,7a-hexahydro-
p-Chloroaniline106-47-8Benzenamine, 4-chloro-
Chlorobenzene108-90-7Benzene, chloro-
Chlorobenzilate510-15-6Benzeneacetic acid, 4-chloro-
-(4-chlorophenyl)-
-hydroxy-, ethyl ester.
p-Chloro-m-cresol; 4-Chloro-3-methylphenol59-50-7Phenol, 4-chloro-3-methyl-
Chloroethane; Ethyl chloride75-00-3Ethane, chloro-
Chloroform; Trichloromethane67-66-3Methane, trichloro-
2-Chloronaphthalene91-58-7Naphthalene, 2-chloro-
2-Chlorophenol95-57-8Phenol, 2-chloro-
4-Chlorophenyl phenyl ether7005-72-3Benzene, 1-chloro-4-phenoxy-
Chloroprene126-99-81,3-Butadiene, 2-chloro-
Chromium(Total)Chromium
Chrysene218-01-9Chrysene
Cobalt(Total)Cobalt
Copper(Total)Copper
m-Cresol; 3-Methylphenol108-39-4Phenol, 3-methyl-
o-Cresol; 2-Methylphenol95-48-7Phenol, 2-methyl-
p-Cresol; 4-Methylphenol106-44-5Phenol, 4-methyl-
Cyanide57-12-5Cyanide
2,4-D; 2,4-Dichlorophenoxyacetic acid94-75-7Acetic acid, (2,4-dichlorophenoxy)-
4,4′-DDD72-54-8Benzene 1,1′-(2,2-dichloroethylidene) bis[4-chloro-
4,4′-DDE72-55-9Benzene, 1,1′-(dichloroethenylidene) bis[4-chloro-
4,4′-DDT50-29-3Benzene, 1,1′-(2,2,2-trichloroethylidene) bis[4-chloro-
Diallate2303-16-4Carbamothioic acid, bis(1-methylethyl)-, S- (2,3-dichloro-2-propenyl) ester.
Dibenz[a,h]anthracene53-70-3Dibenz[a,h]anthracene
Dibenzofuran132-64-9Dibenzofuran
Dibromochloromethane; Chlorodibromomethane124-48-1Methane, dibromochloro-
1,2-Dibromo-3-chloropropane; DBCP96-12-8Propane, 1,2-dibromo-3-chloro-
1,2-Dibromoethane; Ethylene dibromide; EDB106-93-4Ethane, 1,2-dibromo-
Di-n-butyl phthalate84-74-21,2-Benzenedicarboxylic acid, dibutyl ester
o-Dichlorobenzene; 1,2-Dichlorobenzene95-50-1Benzene, 1,2-dichloro-
m-Dichlorobenzene; 1,3-Dichlorobenzene541-73-1Benzene, 1,3-dichloro-
p-Dichlorobenzene; 1,4-Dichlorobenzene106-46-7Benzene, 1,4-dichloro-
3,3′-Dichlorobenzidine91-94-1[1,1′-Biphenyl]-4,4′-diamine, 3,3′-dichloro-
trans-1,4-Dichloro-2-butene110-57-62-Butene, 1,4-dichloro-, (E)-
Dichlorodifluoromethane; CFC 1275-71-8Methane, dichlorodifluoro-
1,1-Dichloroethane; Ethyldidene chloride75-34-3Ethane, 1,1-dichloro-
1,2-Dichloroethane; Ethylene dichloride107-06-2Ethane, 1,2-dichloro-
1,1-Dichloroethylene; 1,1-Dichloroethene;75-35-4Ethene, 1,1-dichloro-
Vinylidene chloride cis-1,2-Dichloroethylene; cis-1,2-Dichloroethene156-59-2Ethene, 1,2-dichloro-(Z)-
trans-1,2-Dichloroethylene; trans-1,2-Dichloroethene156-60-5Ethene, 1,2-dichloro-, (E)-
2,4-Dichlorophenol120-83-2Phenol, 2,4-dichloro-
2,6-Dichlorophenol87-65-0Phenol, 2,6-dichloro-
1,2-Dichloropropane78-87-5Propane, 1,2-dichloro-
1,3-Dichloropropane; Trimethylene dichloride142-28-9Propane, 1,3-dichloro-
2,2-Dichloropropane; Isopropylidene chloride594-20-7Propane, 2,2-dichloro-
1,1-Dichloropropene563-58-61-Propene, 1,1-dichloro-
cis-1,3-Dichloropropene10061-01-51-Propene, 1,3-dichloro-, (Z)-
trans-1,3-Dichloropropene10061-02-61-Propene, 1,3-dichloro-, (E)-
Dieldrin60-57-12,7:3,6-Dimethanonaphth [2,3-b]oxirene, 3,4,5,6,9,9-hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-, (1aα,2β,2aα,3β,6β,6aα,7β,7aα)-
Diethyl phthalate84-66-21,2-Benzenedicarboxylic acid, diethyl ester
O,O-Diethyl O-2-pyrazinyl phosphorothioate; Thionazin297-97-2Phosphorothioic acid, O,O-diethyl O-pyrazinyl ester.
Dimethoate60-51-5Phosphorodithioic acid, O,O-dimethyl S-[2-(methylamino)-2-oxoethyl] ester
p-(Dimethylamino)azobenzene60-11-7Benzenamine, N,N-dimethyl-4-(phenylazo)-
7,12-Dimethylbenz[a]anthracene57-97-6Benz[a]anthracene, 7,12-dimethyl-
3,3′-Dimethylbenzidine119-93-7[1,1′-Biphenyl]-4,4′-diamine, 3,3′-dimethyl-
alpha, alpha-Dimethylphenethylamine122-09-8Benzeneethanamine, α,α-dimethyl-
2,4-Dimethylphenol; m-Xylenol105-67-9Phenol, 2,4-dimethyl-
Dimethyl phthalate131-11-31,2-Benzenedicarboxylic acid, dimethyl ester
m-Dinitrobenzene99-65-0Benzene, 1,3-dinitro-
4,6-Dinitro-o-cresol; 4,6-Dinitro-2-methylphenol534-52-1Phenol, 2-methyl-4,6-dinitro-
2,4-Dinitrophenol51-28-5Phenol, 2,4-dinitro-
2,4-Dinitrotoluene121-14-2Benzene, 1-methyl-2,4-dinitro-
2,6-Dinitrotoluene606-20-2Benzene, 2-methyl-1,3-dinitro-
Dinoseb; DNBP; 2-sec-Butyl-4,6-dinitrophenol88-85-7Phenol, 2-(1-methylpropyl)-4,6-dinitro-
Di-n-octyl phthalate117-84-01,2-Benzenedicarboxylic acid, dioctyl ester
Diphenylamine122-39-4Benzenamine, N-phenyl-
Disulfoton298-04-4Phosphorodithioic acid, O,O-diethyl S-[2- (ethylthio)ethyl] ester
Endosulfan I959-98-86,9-Methano-2,4,3-benzodiox-athiepin, 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-, 3-oxide,
Endosulfan II33213-65-96,9-Methano-2,4,3-benzodioxathiepin, 6,7,8,9,10,10-hexachloro- 1,5,5a,6,9,9a-hexahydro-, 3-oxide, (3α,5aα,6β,9β, 9aα)-
Endosulfan sulfate1031-07-86,9-Methano-2,4,3-benzodioxathiepin, 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-, 3,3-dioxide
Endrin72-20-82,7:3,6-Dimethanonaphth[2,3-b]oxirene, 3,4,5,6,9,9-hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-, (1aα, 2β,2aβ, 3α,6α,6aβ,7β,7aα)-
Endrin aldehyde7421-93-41,2,4-Methenocyclo-penta[cd]pentalene-5-carboxaldehyde,2,2a,3,3,4,7-hexachlorodecahydro- (1α,2β,2aβ,4β,4aβ,5β,6aβ,6bβ,7R*)-
Ethylbenzene100-41-4Benzene, ethyl-
Ethyl methacrylate97-63-22-Propenoic acid, 2-methyl-, ethyl ester
Ethyl methanesulfonate62-50-0Methanesulfonic acid, ethyl ester
Famphur52-85-7Phosphorothioic acid, O-[4-[(dimethylamino)sulfonyl]phenyl]-O,O-dimethyl ester
Fluoranthene206-44-0Fluoranthene
Fluorene86-73-79H-Fluorene
Heptachlor76-44-84,7-Methano-1H-indene,1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-
Heptachlor epoxide1024-57-32,5-Methano-2H-indeno[1,2-b]oxirene,
2,3,4,5,6,7,7-heptachloro-1a,1b,5,5a,6,6a,-hexahydro-,(1aα,1bβ,2α,5α,5aβ,6β,6aα)
Hexachlorobenzene118-74-1Benzene, hexachloro-
Hexachlorobutadiene87-68-31,3-Butadiene, 1,1,2,3,4,4-hexachloro-
Hexachlorocyclopentadiene77-47-41,3-Cyclopentadiene, 1,2,3,4,5,5-hexachloro-
Hexachloroethane67-72-1Ethane, hexachloro-
Hexachloropropene1888-71-71-Propene, 1,1,2,3,3,3-hexachloro-
2-Hexanone; Methyl butyl ketone591-78-62-Hexanone
Indeno(1,2,3-cd)pyrene193-39-5Indeno[1,2,3-cd]pyrene
Isobutyl alcohol78-83-11-Propanol, 2-methyl-
Isodrin465-73-61,4,5,8-Dimethanonaphthalene,1,2,3,4,1 0,10-hexachloro-1,4,4a,5,8,8a hexahydro-(1α, 4α, 4aβ,5β,8β,8aβ)-
Isophorone78-59-12-Cyclohexen-1-one, 3,5,5-trimethyl-
Isosafrole120-58-11,3-Benzodioxole, 5-(1-propenyl)-
Kepone143-50-01,3,4-Metheno-2H-cyclobuta-[cd]pentalen-2-one, 1,1a,3,3a,4,5,5,5a,5b,6-decachlorooctahydro-
Lead(Total)Lead
Mercury(Total)Mercury
Methacrylonitrile126-98-72-Propenenitrile, 2-methyl-
Methapyrilene91-80-51,2,Ethanediamine, N,N-dimethyl-N′-2-pyridinyl-N′-(2-thienylmethyl)-
Methoxychlor72-43-5Benzene, 1,1′-(2,2,2,trichloroethylidene)bis [4-methoxy-
Methyl bromide; Bromomethane74-83-9Methane, bromo-
Methyl chloride; Chloromethane74-87-3Methane, chloro-
3-Methylcholanthrene56-49-5Benz[j]aceanthrylene, 1,2-dihydro-3-methyl-
Methyl ethyl ketone; MEK; 2-Butanone78-93-32-Butanone
Methyl iodide; Iodomethane74-88-4Methane, iodo-
Methyl methacrylate80-62-62-Propenoic acid, 2-methyl-, methyl ester
Methyl methanesulfonate66-27-3Methanesulfonic acid, methyl ester
2-Methylnaphthalene91-57-6Naphthalene, 2-methyl-
Methyl parathion; Parathion methyl298-00-0Phosphorothioic acid, O,O-dimethyl
4-Methyl-2-pentanone; Methyl isobutyl ketone108-10-12-Pentanone, 4-methyl-
Methylene bromide; Dibromomethane74-95-3Methane, dibromo-
Methylene chloride; Dichloromethane75-09-2Methane, dichloro-
Naphthalene91-20-3Naphthalene
1,4-Naphthoquinone130-15-41,4-Naphthalenedione
1-Naphthylamine134-32-71-Naphthalenamine
2-Naphthylamine91-59-82-Naphthalenamine
Nickel(Total)Nickel
o-Nitroaniline; 2-Nitroaniline88-74-4Benzenamine, 2-nitro-
m-Nitroaniline; 3-Nitroaniline99-09-2Benzenamine, 3-nitro-
p-Nitroaniline; 4-Nitroaniline100-01-6Benzenamine, 4-nitro-
Nitrobenzene98-95-3Benzene, nitro-
o-Nitrophenol; 2-Nitrophenol88-75-5Phenol, 2-nitro-
p-Nitrophenol; 4-Nitrophenol100-02-7Phenol, 4-nitro-
N-Nitrosodi-n-butylamine924-16-31-Butanamine, N-butyl-N-nitroso-
N-Nitrosodiethylamine55-18-5Ethanamine, N-ethyl-N-nitroso-
N-Nitrosodimethylamine62-75-9Methanamine, N-methyl-N-nitroso-
N-Nitrosodiphenylamine86-30-6Benzenamine, N-nitroso-N-phenyl-
N-Nitrosodipropylamine; N-Nitroso-N-dipropylamine; Di-n-propylnitrosamine621-64-71-Propanamine, N-nitroso-N-propyl-
N-Nitrosomethylethalamine10595-95-6Ethanamine, N-methyl-N-nitroso-
N-Nitrosopiperidine100-75-4Piperidine, 1-nitroso-
N-Nitrosopyrrolidine930-55-2Pyrrolidine, 1-nitroso-
5-Nitro-o-toluidine99-55-8Benzenamine, 2-methyl-5-nitro-
Parathion56-38-2Phosphorothioic acid, O,O-diethyl-O-(4-nitrophenyl) ester
Pentachlorobenzene608-93-5Benzene, pentachloro-
Pentachloronitrobenzene82-68-8Benzene, pentachloronitro-
Pentachlorophenol87-86-5Phenol, pentachloro-
Phenacetin62-44-2Acetamide, N-(4-ethoxyphenyl)
Phenanthrene85-01-8Phenanthrene
Phenol108-95-2Phenol
p-Phenylenediamine106-50-31,4-Benzenediamine
Phorate298-02-2Phosphorodithioic acid, O,O-diethyl S- [(ethylthio)methyl] ester
Polychlorinated biphenyls; PCBsSee footnote 61,1′-Biphenyl, chloro derivatives
Pronamide23950-58-5Benzamide, 3,5-dichloro-N-(1,1-dimethyl-2-propynyl)-
Propionitrile; Ethyl cyanide107-12-0Propanenitrile
Pyrene129-00-0Pyrene
Safrole94-59-71,3-Benzodioxole, 5-(2- propenyl)-
Selenium(Total)Selenium
Silver(Total)Silver
Silvex; 2,4,5-TP93-72-1Propanoic acid, 2-(2,4,5- trichlorophenoxy)-
Styrene100-42-5Benzene, ethenyl-
Sulfide18496-25-8Sulfide
2,4,5-T; 2,4,5-Trichlorophenoxyacetic acid93-76-5Acetic acid, (2,4,5- trichlorophenoxy)-
2,3,7,8-TCDD; 2,3,7,8-Tetrachlorodibenzo- p-dioxin1746-01-6Dibenzo[b,e][1,4]dioxin, 2,3,7,8-tetrachloro-
1,2,4,5-Tetrachlorobenzene95-94-3Benzene, 1,2,4,5-tetrachloro-
1,1,1,2-Tetrachloroethane630-20-6Ethane, 1,1,1,2-tetrachloro-
1,1,2,2-Tetrachloroethane79-34-5Ethane, 1,1,2,2-tetrachloro-
Tetrachloroethylene; Tetrachloroethene; Perchloroethylene127-18-4Ethene, tetrachloro-
2,3,4,6-Tetrachlorophenol58-90-2Phenol, 2,3,4,6-tetrachloro-
Thallium(Total)Thallium
Tin(Total)Tin
Toluene108-88-3Benzene, methyl-
o-Toluidine95-53-4Benzenamine, 2-methyl-
ToxapheneSee footnote 7Toxaphene
1,2,4-Trichlorobenzene120-82-1Benzene, 1,2,4-trichloro-
1,1,1-Trichloroethane; Methylchloroform71-55-6Ethane, 1,1,1-trichloro-
1,1,2-Trichloroethane79-00-5Ethane, 1,1,2-trichloro-
Trichloroethylene; Trichloroethene79-01-6Ethene, trichloro-
Trichlorofluoromethane; CFC-1175-69-4Methane, trichlorofluoro-
2,4,5-Trichlorophenol95-95-4Phenol, 2,4,5-trichloro-
2,4,6-Trichlorophenol88-06-2Phenol, 2,4,6-trichloro-
1,2,3-Trichloropropane96-18-4Propane, 1,2,3-trichloro-
O,O,O-Triethyl phosphorothioate126-68-1Phosphorothioic acid, O,O,O-triethyl ester
sym-Trinitrobenzene99-35-4Benzene, 1,3,5-trinitro-
Vanadium(Total)Vanadium
Vinyl acetate108-05-4Acetic acid, ethenyl ester
Vinyl chloride; Chloroethene75-01-4Ethene, chloro-
Xylene (total)See footnote 8Benzene, dimethyl-
Zinc(Total)Zinc

1 Common names are those widely used in government regulations, scientific publications, and commerce; synonyms exist for many chemicals.

2 Chemical Abstracts Service registry number. Where “Total” is entered, all species in the ground water that contain this element are included.

3 CAS index names are those used in the 9th Cumulative Index.

4 This substance is often called bis(2-chloroisopropyl) ether, the name Chemical Abstracts Service applies to its noncommercial isomer, propane, 2,2″-oxybis[2-chloro-(CAS RN 39638-32-9).

5 Chlordane: This entry includes alpha-chlordane (CAS RN 5103-71-9), beta-chlordane (CAS RN 5103-74-2), gamma-chlordane (CAS RN 5566-34-7), and constituents of chlordane (CAS RN 57-74-9 and CAS RN 12789-03-6).

6 Polychlorinated biphenyls (CAS RN 1336-36-3); this category contains congener chemicals, including constituents of Aroclor-1016 (CAS RN 12674-11-2), Aroclor-1221 (CAS RN 11104-28-2), Aroclor-1232 (CAS RN 11141-16-5), Aroclor-1242 (CAS RN 53469-21-9), Aroclor-1248 (CAS RN 12672-29-6), Aroclor-1254 (CAS RN 11097-69-1), and Aroclor-1260 (CAS RN 11096-82-5).

7 Toxaphene: This entry includes congener chemicals contained in technical toxaphene (CAS RN 8001-35-2), i.e., chlorinated camphene.

8 Xylene (total): This entry includes o-xylene (CAS RN 96-47-6), m-xylene (CAS RN 108-38-3), p-xylene (CAS RN 106-42-3), and unspecified xylenes (dimethylbenzenes) (CAS RN 1330-20-7).

[70 FR 34556, June 14, 2005; 70 FR 44150, Aug. 1, 2005]
authority: 33 U.S.C. 1345(d) and (e); 42 U.S.C. 6902(a), 6907, 6912(a), 6944, 6945(c) and 6949a(c), 6981(a)
source: 56 FR 51016, Oct. 9, 1991, unless otherwise noted.
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