Final Fifth Contaminant Candidate List Issued By EPA

The U.S. Environmental Protection Agency (EPA) published its Final Fifth Contaminant Candidate List (CCL 5) on November 14, 2022. In this blog post, we review the CCL and take a look at the chemicals and other substances on the list’s most recent version.

CCL 5 Chemical Substances

The presence of harmful substances in drinking water has long been a topic of public debate and is one of ongoing concern. A diverse range of drinking water contaminant types exists, including chemical, biological, physical, and radiological contaminants. Of all possible contaminant types, only a relatively small number of them are found on the CCL.

Containing contaminants present in drinking water systems, CCL chemicals and other substances generally are not covered by existing EPA regulations. Since its initial development more than two decades ago, the CCL has undergone several iterations. The most recent of these includes:

  • 81 contaminants or contaminant groups
    • 69 chemicals or chemical groups
      • 66 chemicals
      • 1 group of cyanotoxins
      • 1 disinfection byproduct group
      • 1 per- and polyfluoroalkyl substances (PFAS) group
    • 12 microbes
      • 8 bacteria
      • 1 protozoa
      • 3 viruses

The CCL 5 chemical contaminants are displayed in the table below:

Substance NameCAS Number
1,2,3-Trichloropropane96-18-4
1,4-Dioxane123-91-1
17-alpha ethynyl estradiol57-63-6
2,4-Dinitrophenol51-28-5
2-Aminotoluene95-53-4
2-Hydroxyatrazine2163-68-0
4-Nonylphenol (all isomers)25154-52-3
6-Chloro-1,3,5-triazine-2,4-diamine3397-62-4
Acephate30560-19-1
Acrolein107-02-8
alpha-Hexachlorocyclohexane (alpha-HCH)319-84-6
Anthraquinone84-65-1
Bensulide741-58-2
Bisphenol A80-05-7
Boron7440-42-8
Bromoxynil1689-84-5
Carbaryl63-25-2
Carbendazim (MBC)10605-21-7
Chlordecone (Kepone)143-50-0
Chlorpyrifos2921-88-2
Cobalt7440-48-4
CyanotoxinsMultiple
Deethylatrazine6190-65-4
Desisopropyl atrazine1007-28-9
Desvenlafaxine93413-62-8
Diazinon333-41-5
Dicrotophos141-66-2
Dieldrin60-57-1
Dimethoate60-51-5
Disinfection byproducts (DBPs)Multiple
Diuron330-54-1
Ethalfluralin55283-68-6
Ethoprop13194-48-4
Fipronil120068-37-3
Fluconazole86386-73-4
Flufenacet142459-58-3
Fluometuron2164-17-2
Iprodione36734-19-7
Lithium7439-93-2
Malathion121-75-5
Manganese7439-96-5
Methomyl16752-77-5
Methyl tert-butyl ether (MTBE)1634-04-4
Methylmercury22967-92-6
Molybdenum7439-98-7
Norflurazon27314-13-2
Oxyfluorfen42874-03-3
Per- and polyfluoroalkyl substances (PFAS)Multiple
Permethrin52645-53-1
Phorate298-02-2
Phosmet732-11-6
Phostebupirim96182-53-5
Profenofos41198-08-7
Propachlor1918-16-7
Propanil709-98-8
Propargite2312-35-8
Propazine139-40-2
Propoxur114-26-1
Quinoline91-22-5
Tebuconazole107534-96-3
Terbufos13071-79-9
Thiamethoxam153719-23-4
Tri-allate2303-17-5
Tribufos78-48-8
Tributyl phosphate126-73-8
Trimethylbenzene (1,2,4-)95-63-6
Tris(2-chloroethyl) phosphate (TCEP)115-96-8
Tungsten7440-33-7
Vanadium7440-62-2

Source: Environmental Protection Agency

The presence of PFAS on the CCL is of particular note, as they are included as a complete class. This inclusion is intended as a key step to enable future research into any of several thousand PFAS chemicals.

Subsequent regulation may be necessary for substances on the list under the Safe Drinking Water Act (SDWA), the law authorizing the establishment of health-based standards to protect against numerous potential drinking water contaminants.

A complete list of all substances on the CCL, both the current version and previous ones, may be found on the EPA website.

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