What’s in My Water? Drinking Water Contaminant List

Here is a list of the regulated and unregulated contaminants in United States drinking water, as per the Environmental Protection Agency (EPA). The top table is of priority pollutants while the bottom has unregulated contaminants, as defined by the UCMR4 list.

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Priority Drinking Water Contaminants

Any pollutant with a (P) next to it is a considered of the foremost priority.

Pollutant CAS Number Human Health for the consumption of Water + Organism
(µg/L)
Organoleptic Effect Criteria
(µg/L)
Publication Year Notes
Acenaphthene (P) 83329 70 20 2015
Acrolein (P) 107028 3 2015
Acrylonitrile (P) 107131 0.061 2015
Aldrin (P) 309002 0.00000077 2015
alpha-Hexachlorocyclohexane (HCH) (P) 319846 0.00036 2015
alpha-Endosulfan (P) 959988 20 2015
Anthracene (P) 120127 300 2015
Antimony (P) 7440360 5.6 1980
Arsenic (P) 7440382 0.018 1992 Refers to the inorganic form only.
Asbestos (P) 1332214 7 million fibers/L 1991
Barium 7440393 1,000 1986
Benzene (P) 71432 0.58-2.1 2015  

 

Benzidine (P) 92875 0.00014 2015
Benzo(a)anthracene (P) 56553 0.0012 2015
Benzo(a)pyrene (P) 50328 0.00012 2015
Benzo(b)fluoranthene (P) 205992 0.0012 2015
Benzo(k)fluoranthene (P) 207089 0.012 2015
Beryllium (P) 7440417
beta-Hexachlorocyclohexane (HCH) (P) 319857 0.0080 2015
beta-Endosulfan (P) 33213659 20 2015
Bis(2-Chloro-1-methylethyl) Ether (P) 108601 200 2015
Bis(2-Chloroethyl) Ether (P) 111444 0.030 2015
Bis(2-Ethylhexyl) Phthalate (P) 117817 0.32 2015
Bis(Chloromethyl) Ether 542881 0.00015 2015
Bromoform (P) 75252 7.0 2015  

 

Butylbenzyl Phthalate (P) 85687 0.10 2015
Cadmium (P) 7440439
Carbon Tetrachloride (P) 56235 0.4 2015  

 

Chlordane (P) 57749 0.00031 2015
Chlorobenzene (P) 108907 100 2015
Chlorodibromomethane (P) 124481 0.80 2015  

 

Chloroform (P) 67663 60 2015
Chlorophenoxy Herbicide (2,4-D) 94757 1,300 2015
Chlorophenoxy Herbicide (2,4,5-TP) [Silvex] 93721 100 2015
Chromium (III) (P) 16065831 Total
Chromium (VI) (P) 18540299 Total
Chrysene (P) 218019 0.12 2015
Copper (P) 7440508 1,300 1000 1992
Cyanide (P) 57125 4 2015
Dibenzo(a,h)anthracene (P) 53703 0.00012 2015
Dichlorobromomethane (P) 75274 0.95 2015
Dieldrin (P) 60571 0.0000012 2015
Diethyl Phthalate (P) 84662 600 2015
Dimethyl Phthalate (P) 131113 2,000 2015
Di-n-Butyl Phthalate (P) 84742 20 2015
Dinitrophenols 25550587 10 2015
Endosulfan Sulfate (P) 1031078 20 2015
Endrin (P) 72208 0.03 2015
Endrin Aldehyde (P) 7421934 1 2015
Ethylbenzene (P) 100414 68 2015
Fluoranthene (P) 206440 20 2015
Fluorene (P) 86737 50 2015
gamma-Hexachlorocyclohexane (HCH) [Lindane] (P) 58899 4.2 2015
Heptachlor (P) 76448 0.0000059 2015
Heptachlor Epoxide (P) 1024573 0.000032 2015
Hexachlorobenzene (P) 118741 0.000079 2015
Hexachlorobutadiene (P) 87683 0.01 2015
Hexachlorocyclohexane (HCH) -Technical 608731 0.0066 2015
Hexachlorocyclopentadiene (P) 77474 4 2015
Hexachloroethane (P) 67721 0.1 2015
Indeno(1,2,3-cd)pyrene (P) 193395 0.0012 2015
Isophorone (P) 78591 34 2015
Manganese 7439965 50 1993
Methylmercury (P) 22967926 2001
Methoxychlor 72435 0.02 2015
Methyl Bromide (P) 74839 100 2015
Methylene Chloride (P) 75092 20 2015
Nickel (P) 7440020 610 1998
Nitrates 14797558 10,000 1986
Nitrobenzene (P) 98953 10 30 2015
Nitrosamines 0.0008 1980
Nitrosodibutylamine 924163 0.0063 2002
Nitrosodiethylamine 55185 0.0008 2002
Nitrosopyrrolidine 930552 0.016 2002
N-Nitrosodimethylamine (P) 62759 0.00069 2002
N-Nitrosodi-n-Propylamine (P) 621647 0.0050 2002
N-Nitrosodiphenylamine (P) 86306 3.3 2002
Pentachlorobenzene 608935 0.1 2015
Pentachlorophenol (P) 87865 0.03 30 2015  

 

 

pH 5 – 9 1986
Phenol (P) 108952 4,000 300 2015
Polychlorinated Biphenyls (PCBs) (P) 0.000064 2002  

 

 

Pyrene (P) 129000 20 2015
Selenium (P) 7782492 170 2002
Solids Dissolved and Salinity 250,000 1986
Tetrachloroethylene (P) 127184 10 2015  

 

Thallium (P) 7440280 0.24 2003
Toluene (P) 108883 57 2015
Toxaphene (P) 8001352 0.00070 2015
Trichloroethylene (P) 79016 0.6 2015
Vinyl Chloride (P) 75014 0.022 2015
Zinc (P) 7440666 7,400 5000 2002
1,1,1-Trichloroethane (P) 71556 10,000 2015
1,1,2,2-Tetrachloroethane (P) 79345 0.2 2015
1,1,2-Trichloroethane (P) 79005 0.55 2015
1,1-Dichloroethylene (P) 75354 300 2015
1,2,4,5-Tetrachlorobenzene 95943 0.03 2015
1,2,4-Trichlorobenzene (P) 120821 0.071 2015
1,2-Dichlorobenzene (P) 95501 1,000 2015
1,2-Dichloroethane (P) 107062 9.9 2015
1,2-Dichloropropane (P) 78875 0.90 2015
1,2-Diphenylhydrazine (P) 122667 0.03 2015
Trans-1,2-Dichloroethylene (P) 156605 100 2015
1,3-Dichlorobenzene (P) 541731 7 2015
1,3-Dichloropropene (P) 542756 0.27 2015
1,4-Dichlorobenzene (P) 106467 300 2015
2,3,7,8-TCDD (Dioxin) (P) 1746016 5.0E-9 2002
2,4,5-Trichlorophenol 95954 300 1 2015
2,4,6-Trichlorophenol (P) 88062 1.5 2 2015
2,4-Dichlorophenol (P) 120832 10 0.3 2015
2,4-Dimethylphenol (P) 105679 100 400 2015
2,4-Dinitrophenol (P) 51285 10 2015
2,4-Dinitrotoluene (P) 121142 0.049 2015
2-Chloronaphthalene (P) 91587 800 2015
2-Chlorophenol (P) 95578 30 0.1 2015
2-Methyl-4,6-Dinitrophenol (P) 534521 2 2015
3,3′-Dichlorobenzidine (P) 91941 0.049 2015
3-Methyl-4-Chlorophenol (P) 59507 500 3000 2015
p,p′-Dichlorodiphenyldichloroethane (DDD) (P) 72548 0.00012 2015
p,p′-Dichlorodiphenyldichloroethylene (DDE) (P) 72559 0.000018 2015
p,p′-Dichlorodiphenyltrichloroethane (DDT) (P) 50293 0.000030 2015

The source of this list is the EPA.gov website.

Unregulated Chemical Contaminants

This is a list of US government-recognized water contaminants. These are know as unregulated contaminants because they are not currently subject to regulations but a recognized as being present in the water supply and harmful to humans. Future updates to the Safe Drinking Water Act (SDWA) may include the contaminants as regulated chemicals if they are deemed to pose a significant enough risk to public health.

The source of this data is the Contaminant Candidate List (CCL), version 4, which was established in 2016. The CAS Registry Number (CASRN or CAS#), is a identifier for a unique chemical compound as labeled by the Chemical Abstracts Service. Below this list we’ll include a list of the microbial (living), unregulated contaminants found in the water supply. The source of the list is also the CCL4.

Name
CAS#
Use
1,1-Dichloroethane
75-34-3 Industrial solvent and an intermediate in the synthesis of other compounds.
1,1,1,2-Tetrachloroethane
630-20-6
Industrial solvent and used in the synthesis of other chlorinated compounds.
1,2,3-Trichloropropane
96-18-4
Industrial solvent, cleaning and degreasing agent as well as an intermediate in the synthesis of the other compounds.
1,3-Butadiene
106-99-0
Used in the production of rubber and plastics.
1,4-Dioxane
123-91-1
A solvent for cellulose formulations, resins, oils, waxes and other organic substances. It is also used in wood pulping, textile processing, degreasing, in lacquers, paints, varnishes, and stains; and in paint and varnish removers.
17alpha-estradiol
57-91-0
Estrogenic hormone found in some pharmaceuticals.
1-Butanol
71-36-3
A solvent and used in production of other chemicals. compounds.  It is present in a number of commercial products such as perfumes.
2-Methoxyethanol
109-86-4
Used in a number of consumer products, such as synthetic cosmetics, perfumes, fragrances, hair preparations, and skin lotions.
2-Propen-1-ol
107-18-6
Used in the production of other chemicals.
3-Hydroxycarbofuran
16655-82-6
A pesticide degradate, the parent, carbofuran, is used as an insecticide.
4,4′-Methylenedianiline
101-77-9
It is used in the production of polyurethanes foams, glues, rubber and spandex fiber.
Acephate
30560-19-1
It is an insecticide.
Acetaldehyde
75-07-0
It is a disinfection byproduct from ozonation; it is used in the production of other chemicals.
Acetamide
60-35-5
It is used as a solvent and plasticizer.
Acetochlor
34256-82-1
It is an herbicide for weed control on agricultural crops.
Acetochlor ethanesulfonic acid (ESA)
187022-11-3
Acetochlor ESA is an environmental degradate of acetochlor.
Acetochlor oxanilic acid (OA)
184992-44-4
Acetochlor OA is an environmental degradate of acetochlor.
Acrolein
107-02-8
It is used as an aquatic herbicide, rodenticide and industrial chemical.
Alachlor ethanesulfonic acid (ESA)
142363-53-9
Alachlor ESA is an environmental degradate of the pesticide alachlor (an herbicide for weed control on agricultural crops).
Alachlor oxanilic acid (OA)
171262-17-2
Alachlor OA is an environmental degradate of alachlor.
alpha-Hexachlorocyclohexane
319-84-6
It is a component of benzene hexachloride (BHC) and was formerly used as an insecticide.
Aniline
62-53-3
It is used as an industrial chemical, as a solvent, in the synthesis of explosives, rubber products and in isocyanates.
Bensulide
741-58-2
It is an herbicide.
Benzyl chloride
100-44-7
It is used in the production of other substances, such as plastics, dyes, lubricants, gasoline and pharmaceuticals.
Butylated hydroxyanisole
25013-16-5
It is used as a food additive (antioxidant).
Captan
133-06-2
It is a fungicide.
Chlorate
14866-68-3
Chlorate compounds are used in agriculture as defoliants or desiccants and may occur in drinking water because of use of disinfectants such as chlorine dioxide and hypochlorites.
Chloromethane (Methyl chloride)
74-87-3
It is used as a foaming agent and in the production of other substances.
Clethodim
110429-62-4
It is an herbicide.
Cobalt
7440-48-4
It is a naturally-occurring element and was formerly used as cobaltous chloride in medicines and as a germicide. It is a part of the vitamin B12 molecule
Cumene hydroperoxide
80-15-9
It is used as a catalyst is used in the production of other substances.
Cyanotoxins
Not applicable.
Toxins naturally produced and released by cyanobacteria (“blue-green algae”). The group of cyanotoxins includes, but is not limited to: anatoxin-a, cylindrospermopsin, microcystins, and saxitoxin.
Dicrotophos
141-66-2
It is an insecticide.
Dimethipin
55290-64-7
It is an herbicide and plant growth regulator.
Diuron
330-54-1
It is an herbicide.
Equilenin
517-09-9
It is an estrogenic hormone used in hormone replacement therapy.
Equilin
474-86-2
It is an estrogenic hormone and is used in hormone replacement therapy.
Erythromycin
114-07-8
It is used an antibiotic.
Estradiol (17-beta estradiol)
50-28-2
It is an isomer of estradiol found in some pharmaceuticals.
Estriol
50-27-1
It is a weak estrogenic hormone used in veterinary pharmaceuticals.
Estrone
53-16-7
It is a precursor of estradiol used in veterinary and human pharmaceuticals.
Ethinyl estradiol (17-alpha ethynyl estradiol)
57-63-6
It is an estrogenic hormone and is used in veterinary and human oral contraceptives.
Ethoprop
13194-48-4
It is an insecticide.
Ethylene glycol
107-21-1
It is used as antifreeze, in textile manufacturing and is a cancelled pesticide.
Ethylene oxide
75-21-8
It is a fungicidal and insecticidal fumigant.
Ethylene thiourea
96-45-7
It is used in the production of other substances, such as for vulcanizing polychloroprene (neoprene) and polyacrylate rubbers and is a metabolite of some fungicides.
Formaldehyde
50-00-0
It is an ozoneation disinfection byproduct, can occur naturally and has been used as a fungicide.
Germanium
7440-56-4
It is a naturally-occurring element and is commonly found as germanium dioxide in phosphors, transistors and diodes, and in electroplating. In some cases it has been sold as a dietary supplement.
HCFC-22
75-45-6
It is used as a refrigerant, as a low-temperature solvent, and in fluorocarbon resins, especially in tetrafluoroethylene polymers.
Halon 1011 (bromochloromethane) 74-97-5
It is used as a fire-extinguishing fluid and to suppress explosions, as well as a solvent in the manufacturing of some pesticides. May also occur as a disinfection by-product in drinking water.
Hexane
110-54-3
It is a component of gasoline and used as a solvent.
Hydrazine
302-01-2
It is used as an ingredient in the production of other substances, such as rocket propellants. It is also used in the production of plastics.
Manganese
7439-96-5
It is a naturally-occurring element used in a variety of applications including use in steel production to improve hardness, stiffness and strength.  It is an essential nutrient found in vitamin/mineral supplement and in fortified foods.
Mestranol
72-33-3
It is a precursor to ethinylestradiol used in veterinary and human pharmaceuticals.
Methamidophos
10265-92-6
It is an insecticide.
Methanol
67-56-1
It is used as an industrial solvent, a gasoline additive and as an anti-freeze ingredient.
Methyl bromide (bromomethane)
74-83-9
It has been used as a fumigant and fungicide.
Methyl tert-butyl ether (MTBE)
1634-04-4
It is used as an octane booster in gasoline, in the manufacturing of isobutene and as an extraction solvent.
Metolachlor
51218-45-2
It is an herbicide for weed control on agricultural crops.
Metolachlor ethanesulfonic acid (ESA)
171118-09-5
Metolachlor ESA is an environmental degradate of metolachlor.
Metolachlor oxanilic acid (OA)
152019-73-3
Metolachlor OA is an environmental degradate of metolachlor.
Molybdenum
7439-98-7
It is a naturally-occurring element and is commonly found as molybdenum trioxide.   It is used as a steel alloy.  It is an essential dietary nutrient found in foods and nutritional supplements.
Nitrobenzene
98-95-3
It is used in the production of aniline, and also as a solvent in the manufacturing of paints, shoe polishes, floor polishes, metal polishes, explosives, dyes, pesticides and drugs (such as acetaminophen).,
Nitroglycerin
55-63-0
It is used in the production of explosives, and in rocket propellants. It is also a pharmaceutical for the treatment of angina.
N-Methyl-2-pyrrolidone
872-50-4
It is a solvent in the chemical industry, and is used in the formulation of pharmaceuticals for oral and dermal delivery.
N-nitrosodiethylamine (NDEA)
55-18-5
It is a nitrosamine used as an additive in gasoline and in lubricants, as an antioxidant and as a stabilizer in plastics. It is formed in cured foods and during high temperature cooking of meats and fish, and may be a disinfection byproduct.
N-nitrosodimethylamine (NDMA)
62-75-9
It was formerly used in the production of rocket fuels, anti-oxidants and softeners for copolymers. It is formed in cured foods and during high temperature cooking. It may be a leachate from rubber gaskets and fittings and may form as a disinfection byproduct.
N-nitroso-di-n-propylamine (NDPA)
621-64-7
It is formed in cured foods and during high temperature cooking of meats and fish and may be a disinfection byproduct.  It is a contaminant in dinitrofluralin herbicides.
N-Nitrosodiphenylamine
86-30-6
It is used in the vulcanization of rubber and as an inhibitor of polymerization in the production of polystyrene. It may be a disinfection byproduct.
N-nitrosopyrrolidine (NPYR)
930-55-2
It is used in rubber production. It is formed in cured foods and during high temperature cooking of meats and fish and may be a disinfection byproduct.
Nonylphenol2
25154-52-3
The main use of nonylphenol is in the manufacture of nonylphenol ethoxylates, which have been used in a wide range of industrial applications and consumer products including laundry detergents, cleaners, degreasers, paints and coatings and other uses. Several other CASRNs are associated with nonyphenol due to varying chemical structures including: 104-40-5, 84852-15-3, 91672-41-2, and 139-84-4.
Norethindrone (19-Norethisterone)
68-22-4
Norethindrone is a synthetic hormone used in oral contraceptives and for hormone replacement therapy.
n-Propylbenzene
103-65-1
It is a constituent of asphalt and naptha and used in the manufacture of methyl styrene. It is a solvent for printing and dying of textiles.
o-Toluidine
95-53-4
It is used in the production of dyes, rubber, pharmaceuticals and pesticides.
Oxirane, methyl
75-56-9
It is an industrial chemical used in the production of other substances. It is a registered pesticide.
Oxydemeton-methyl
301-12-2
It is an insecticide.
Oxyfluorfen
42874-03-3
It is an herbicide.
Perfluorooctanesulfonic acid (PFOS)
1763-23-1
PFOS has been used to make carpets, leathers, textiles, fabrics for furniture, paper packaging, and other materials that are resistant to water, grease, or stains. It is also used in firefighting foams at airfields. Many of these uses have been phased out by its primary U.S. manufacturer; however, there are still some ongoing uses.
Perfluorooctanoic acid (PFOA)
335-67-1
PFOA has been used to make carpets, leathers, textiles, fabrics for furniture, paper packaging, and other materials that are resistant to water, grease, or stains. It is also used in firefighting foams at airfields. Many of these uses are being phased out by U.S. manufacturers; however, there are still some ongoing uses.
Permethrin
52645-53-1
It is an insecticide.
Profenofos
41198-08-7
It is an insecticide and an acaricide.
Quinoline
91-22-5
It is a component of coal tars and used in the production of other substances, and as a pharmaceutical (anti-malarial).
RDX (Hexahydro-1,3,5-trinitro-1,3,5-triazine)
121-82-4
It is an explosive.
sec-Butylbenzene
135-98-8
It is used as a solvent for coatings in organic synthesis, as a plasticizer and in surfactants.
Tebuconazole
107534-96-3
It is a fungicide.
Tebufenozide
112410-23-8
It is insecticide.
Tellurium
13494-80-9
It is a naturally-occurring element and is commonly used as sodium tellurite in bacteriology and medicine.
Thiodicarb
59669-26-0
It is an insecticide.
Thiophanate-methyl
23564-05-8
It is a fungicide.
Toluene diisocyanate
26471-62-5
It is used in the manufacturing of plastics.
Tribufos
78-48-8
It is an insecticide and used as a cotton defoliant.
Triethylamine
121-44-8
It is used in the production of other substances, as a stabilizer in herbicides and pesticides, in consumer products, in photographic chemicals and in carpet cleaners.
Triphenyltin hydroxide (TPTH)
76-87-9
It is a pesticide.
Urethane
51-79-6
It is a paint and coating ingredient (polyurethanes).
Vanadium
7440-62-2
It is a naturally-occurring element.  Vanadium pentoxide is a catalyst for the production of other substances catalyst. It is sometimes an ingredient in mineral supplements but is not classified as an essential nutrient
Vinclozolin
50471-44-8
It is a fungicide.
Ziram
137-30-4
It is a fungicide.

Microbial Contaminants

Microbial Contaminant Name
Type
Diseases and Infections
Adenovirus
Virus
Respiratory illness and occasionally gastrointestinal illness.
Caliciviruses
Virus (includes Norovirus)
Mild self-limiting gastrointestinal illness.
Campylobacter jejuni
Bacteria
Mild self-limiting gastrointestinal illness.
Enterovirus
Virus
Mild respiratory illness.
Escherichia coli (0157)
Bacteria
Gastrointestinal illness and kidney failure.
Helicobacter pylori
Bacteria
Found in the environment capable of colonizing human gut that can cause ulcers and cancer.
Hepatitis A virus
Virus
Liver disease and jaundice.
Legionella pneumophila
Bacteria
Found in the environment including hot water systems causing lung diseases when inhaled.
Mycobacterium avium
Bacteria
Lung infection in those with underlying lung disease, and disseminated infection in the severely immuno compromised.
Naegleria fowleri
Protozoan
Parasite found in shallow, warm surface and ground water causing primary amebic meningoencephalitis.
Salmonella enterica
Bacteria
Mild self-limiting gastrointestinal illness.
Shigella sonnei
Bacteria
Mild self-limiting gastrointestinal illness and bloody diarrhea.

Other Contaminants / Conditions

Contaminants not covered in the aforementioned tables. Most of these are considered under “Secondary Water Standards.”

Contaminant Name
Primary MCL / Seconary MCL (mg/L)
Notes
Iron
None / 0.30
Organoleptic Effect: 300 µg/L
Alkalinity
None / None
Fluoride 4.0 / 2.0
Hardness None / None
Lead 0.015 / None 0.015 mg/L reflects an EPA action level
Magnesium None / None
Mercury 0.002 / None
Nitrite 1.0 / None
pH None / 6.5-8.5
Silver None / 0.1
Sodium None / None