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  2. Contaminant Candidate List (CCL) and Regulatory Determination

Draft CCL 6 Chemical Contaminants

Chemical NameCASRN1DTXSID2
1,2,3-Trichloropropane96-18-4DTXSID9021390
1,2,4-Triazole288-88-0DTXSID6027131
1,2,4-Trimethylbenzene95-63-6DTXSID6021402
1,2-Diphenylhydrazine122-66-7DTXSID7020710
1,4-Dioxane123-91-1DTXSID4020533
1-Methylnaphthalene90-12-0DTXSID9020877
2,4,6-Trinitrotoluene118-96-7DTXSID7024372
2,6-Dinitrotoluene606-20-2DTXSID5020528
4-tert-Octylphenol140-66-9DTXSID9022360
Acephate30560-19-1DTXSID8023846
Acrylonitrile107-13-1DTXSID5020029
alpha-1,2,3,4,5,6-Hexachlorocyclohexane319-84-6DTXSID2020684
Aluminum7429-90-5DTXSID3040273
Anthraquinone84-65-1DTXSID3020095
Bensulide741-58-2DTXSID9032329
Benzyl butyl phthalate85-68-7DTXSID3020205
Bisphenol A80-05-7DTXSID7020182
Bromoxynil1689-84-5DTXSID3022162
Carbaryl63-25-2DTXSID9020247
Carbendazim10605-21-7DTXSID4024729
Chlordecone (Kepone)143-50-0DTXSID1020770
Chloromethane74-87-3DTXSID0021541
Chlorothalonil1897-45-6DTXSID0020319
Chlorpyrifos2921-88-2DTXSID4020458
Clothianidin210880-92-5DTXSID2034465
Cobalt7440-48-4DTXSID1031040
Diazinon333-41-5DTXSID9020407
Dicamba1918-00-9DTXSID4024018
Dichlorvos62-73-7DTXSID5020449
Dicrotophos141-66-2DTXSID9023914
Dithiopyr97886-45-8DTXSID9032379
Diuron330-54-1DTXSID0020446
Ethalfluralin55283-68-6DTXSID8032386
Ethylene thiourea96-45-7DTXSID5020601
Fenbuconazole114369-43-6DTXSID8032548
Fipronil120068-37-3DTXSID4034609
Flufenacet142459-58-3DTXSID2032552
Fluometuron2164-17-2DTXSID8020628
Fluoranthene206-44-0DTXSID3024104
Imazalil35554-44-0DTXSID8024151
Iodide20461-54-5DTXSID80912339
Iprodione36734-19-7DTXSID3024154
Isophorone78-59-1DTXSID8020759
Lithium7439-93-2DTXSID5036761
Malaoxon1634-78-2DTXSID9020790
Malathion121-75-5DTXSID4020791
Manganese7439-96-5DTXSID2024169
Methomyl16752-77-5DTXSID1022267
Methyl mercury22967-92-6DTXSID9024198
Methyl tert-butyl ether (MTBE)1634-04-4DTXSID3020833
Nicotine54-11-5DTXSID1020930
Nitroglycerin55-63-0DTXSID1021407
Nonylphenol25154-52-3DTXSID3021857
Oryzalin19044-88-3DTXSID8024238
Oxadiazon19666-30-9DTXSID3024239
Oxyfluorfen42874-03-3DTXSID7024241
p-Cresol106-44-5DTXSID7021869
Phorate298-02-2DTXSID4032459
Phosmet732-11-6DTXSID5024261
Propargite2312-35-8DTXSID4024276
Quinoline91-22-5DTXSID1021798
Silver7440-22-4DTXSID4024305
Strontium7440-24-6DTXSID3024312
Terbufos13071-79-9DTXSID2022254
tert-Butyl alcohol75-65-0DTXSID8020204
Thiamethoxam153719-23-4DTXSID2034962
Tolyltriazole29385-43-1DTXSID0026171
Tri-allate2302-17-5DTXSID5024344
Tributyl phosphate126-73-8DTXSID3021986
Trifluralin1582-09-8DTXSID4021395
Triphenyl phosphate115-86-6DTXSID1021952
Tris(2-chloroethyl) phosphate115-96-8DTXSID5021411
Tungsten7440-33-7DTXSID8052481
Vanadium7440-62-2DTXSID2040282
Zinc7440-66-6DTXSID7035012

1 Chemical Abstracts Service Registry Number; a unique identifier assigned by the Chemical Abstracts Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic compounds, polymers elements, nuclear particles, etc.) in the open scientific literature. It contains up to 10 digits, separated by hyphens into three parts.

2 Distributed Structure Searchable Toxicity (DSSTox) Substance Identifier; a unique substance identifier assigned in EPA’s CompTox Chemicals Dashboard, where a substance can be any single chemical, mixture or polymer.

Chemical GroupInclusion
Disinfection byproducts (DBPs)Twenty-seven unregulated DBPs (brominated haloacetic acids, haloacetonitriles, halonitromethanes, iodinated trihalomethanes, nitrosamines, and others).
MicroplasticsThere are currently data gaps that require further research before the Agency can fully understand the health risks associated with microplastics in drinking water.
Per- and polyfluoroalkyl substances (PFAS)3

PFAS that contain one of three chemical structures:

  1. R-(CF2)-CF(R′)R′′, where both the CF2 and CF moieties are saturated carbons, and none of the R groups can be hydrogen
  2. R-CF2OCF2-R′, where both the CF2 moieties are saturated carbons, and none of the R groups can be hydrogen
  3. CF3C(CF3)RR′, where all the carbons are saturated, and none of the R groups can be hydrogen
PharmaceuticalsSubstances that meet the definition for a “drug” under the Federal Food, Drug, and Cosmetic Act (21 U.S.C 321).

3Excludes PFAS covered under a national primary drinking water regulation (see National Primary Drinking Water Regulations, Subpart Z - Control of Per- and Polyfluoroalkyl Substances (PFAS))

Contaminant Candidate List (CCL) and Regulatory Determination

  • Basic Information
  • Contaminant Candidate List 6
  • Contaminant Candidate List 5
  • Contaminant Candidate List 4
  • Contaminant Candidate List 3
  • Contaminant Candidate List 2
  • Contaminant Candidate List 1
  • Regulatory Determination 5
  • Regulatory Determination 4
  • Regulatory Determination 3
  • Regulatory Determination 2
  • Regulatory Determination 1
  • Types of Drinking Water Contaminants
Contact Us About the CCL and Regulatory Determinations
Contact Us About the CCL and Regulatory Determinations to ask a question, provide feedback, or report a problem.
Last updated on April 2, 2026
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