National Primary Drinking Water Standards

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Contaminants MCLG
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Fluoride 4.0 4.0 Skeletal and dental fluorosis Natural deposits; fertilizer, aluminum industries; water additive
Volatile Organics
Benzene zero 0.005 Cancer Some foods; gas, drugs, pesticides, paint, plastic industries
Carbon Tetrachloride zero 0.005 Cancer Solvents and their degradation products
p-Dichlorobenzene 0.075 0.075 Cancer Room and water deodorants, and "mothballs"
1,2-Dichloroethane zero 0.005 Cancer Leaded gasoline, fumigants, paints
1,1-Dichloroethylene 0.007 0.007 Cancer Plastics, dyes, perfumes, paints
Trichloroethylene zero 0.005 Cancer Textiles, adhesives and metal degreasers
1,1,1-Trichloroethane 0.2 0.2 Liver, Nervous system effects Adhesives, aerosols, textiles, paints, inks, metal degreasers
Vinyl Chloride zero 0.002 Cancer May leach from PVC pipe; formed by solvent breakdown
Coliform and Surface Water Treatment
Giardia Lamblia zero TT Gastroenteric disease Human and animal fecal waste
Legionella zero TT Legionnaire's disease Indigenous to natural waters; can grow in water heating systems
Standard Plate Count N/A TT Indicates water quality, effectiveness of treatment  
Total Coliform* zero <5%+ Indicates gastroenteric pathogens Human and animal fecal waste
Turbidity* N/A TT Interferes with disinfection, filtration Soil runoff
Viruses zero TT Gastroenteric disease Human and animal fecal waste
Notes: TT=Special treatment techniques required

*Contaminants with interim standards which have been revised.

+=less than 5% positive samples


Contaminants MCLG
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Antimony 0.006 0.006 Cancer Fire retardants, ceramics, electronics, fireworks, solder
Asbestos (>10m) 7MFL 7MFL Cancer Natural deposits; asbestos cement in water systems
Barium* 2 2 Circulatory system effects Natural deposits, pigments, epoxy sealants, spent coal
Beryllium 0.004 0.004 Bone, lung damage Electrical, aerospace, defense industries
Cadmium* 0.005 0.005 Kidney effects Galvanized pipe corrosion; natural deposits; batteries, paints
Chromium* (total) 0.1 0.1 Liver, kidney, circulatory disorders Natural deposits; mining, electroplating, pigments
Cyanide 0.2 0.2 Thyroid, nervous system damage Electroplating, steel, plastics, mining, fertilizer
Mercury* (inorganic) 0.002 0.002 Kidney, nervous system disorders Crop runoff; natural deposits; batteries, electrical switches
Nitrate* 10 10 Methemoglobinemia Animal waste, fertilizer, natural deposits, septic tanks, sewage
Nitrite 1 1 Methemoglobinemia Same as nitrate; rapidly converted to nitrate
Selenium* 0.05 0.05 Liver damage Natural deposits; mining, smelting, coal/oil combustion
Thallium 0.0005 0.002 Kidney, liver, brain, intestinal Electronics, drugs, alloys, glass
Notes: *Contaminants with interim standards which have been revised.

MFL=million fibers per liter.


Contaminants MCLG
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Organics (1of 4)
Acrylamide zero TT Cancer, nervous system effects Polymers used in sewage/wastewater treatment

(di (2-ehtylhexyl)

0.4 0.4 Decreased body weight Synthetic rubber, food packaging, cosmetics
Alachlor zero 0.002 Cancer Runoff from herbicide on corn, soybeans, other crops
Atrazine 0.003 0.003 Mammary gland tumors Runoff from use as herbicide on corn and non-cropland
Carbofuran 0.04 0.04 Nervous, reproductive system effects Soil fumigant on corn and cotton; restricted in some areas
Chlordane* zero 0.002 Cancer Leaching from soil treatment for termites
Chlorobenzene 0.1 0.1 Nervous system and liver effects Waste solvent from metal degreasing processes
Dalapon 0.2 0.2 Liver and kidney effects Herbicide on orchards, beans, coffee, lawns, road/railways
Dibromo chloropropene zero 0.0002 Cancer Soil fumigant on soybeans, cotton, pineapple, orchards
o-Dichlorobenzene 0.6 0.6 Liver, kidney, blood cell damage Paints, engine cleaning compounds, dyes, chemical wastes
cis-1,2-Dichloroethylene 0.07 0.07 Liver, kidney, nervous, circulatory Waste industrial extraction solvents
trans-1,2-Dichloroethylene 0.1 0.1 Liver, kidney, nervous, circulatory Waste industrial extraction solvents
Dichloromethane zero 0.005 Cancer Paint stripper, metal degreaser, propellant, extraction
1,2-Dichloropropane zero 0.005 Liver, kidney effects; cancer Soil fumigant; waste industrial solvents
Notes: *Contaminants with interim standards which have been revised.


Contaminants MCLG
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Organics (2 of 4)
Dinoseb 0.007 0.007 Thyroid, reproductive organ damage Runoff of herbicide from crop and non-crop applications
Dioxin zero 0.00000003 Cancer Chemical production by-product; impurity in herbicides
Diquat 0.02 0.02 Liver, kidney, eye effects Runoff of herbicide on land and aquatic weeds
2,4-D* 0.07 0.07 Liver and kidney damage Runoff from herbicide on wheat, corn, rangelands, lawns
Endothall 0.1 0.1 Liver, kidney, gastrointestinal Herbicide on crops, land/aquatic weeds; rapidly degraded
Endrin 0.002 0.002 Liver, kidney, heart damage Pesticide on insects, rodents, birds; restricted since 1980
Epichlorohydrin zero TT Cancer Water treatment chemicals; waste epoxy resins, coatings
Ethylbenzene 0.7 0.7 Liver, kidney, nervous system Gasoline; insecticides; chemical manufacturing wastes
Ethylene dibromide zero 0.00005 Cancer Leaded gasoline additives; leaching of soil fumigant
Glyphosate 0.7 0.7 Liver, kidney damage Herbicide on grasses, weeds, brush
Heptachlor zero 0.0004 Cancer Leaching of insecticide for termites, very few crops
Heptachlor epoxide zero 0.0002 Cancer Biodegradation of heptachlor
Notes: *Contaminants with interim standards which have been revised.

TT=Special treatment techniques required


Contaminants MCLG
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Organics (3 of 4)
Hexachlorobenzene zero 0.001 Cancer Pesticide production waste by-product
Hexachlorocyclopentadiene 0.05 0.05 Kidney, stomach damage Pesticide production intermediate
Lindane 0.0002 0.0002 Liver, kidney, nervous, immune, circulatory Insecticide on cattle, lumber, gardens; restricted in 1983
Methoxychlor 0.04 0.04 Growth, liver, kidney, nerve effects Insecticide for fruits, vegetables, alfalfa, livestock, pets
Oxamyl (Vydate) 0.2 0.2 Kidney damage Insecticide on apples, potatoes, tomatoes
PAHs (benzo(a)pyrene) zero 0.0002 Cancer Coal tar coatings; burning organic matter; volcanoes, fossil fuels
PCBs zero 0.0005 Cancer Coolant oils from electrical transformers; plasticizers
Pentachlorophenol zero 0.001 Liver and kidney effects, and cancer Wood preservatives, herbicide, cooling tower wastes

(di (2-ethylhexyl))

zero 0.006 Cancer PVC and other plastics
Picloram 0.5 0.5 Kidney, liver damage Herbicide on broadleaf and woody plants
Simazine 0.004 0.004 Cancer Herbicide on grass sod, some crops, aquatic algae
Styrene 0.1 0.1 Liver, nervous system damage Plastics, rubber, resin, drug industries; leachate from city landfills
Tetrachloroethylene zero 0.005 Cancer Improper disposal of dry cleaning and other solvents
Toluene 1 1 Liver, kidney, nervous, circulatory Gasoline additive; manufacturing and solvent operations


Contaminants MCLG
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Organics (4 of 4)
Toxaphene zero 0.003 Cancer Insecticide on cattle, cotton, soybeans; canceled in 1982
2,4,5-TP 0.05 0.05 Liver and kidney damage Herbicide on crops, right-of-way, golf courses; canceled in 1983
1,2,4-Trichlorobenzene 0.07 0.07 Liver, kidney damage Herbicide production, dye carrier
1,1,2-Trichloroethane 0.003 0.005 Kidney, liver, nervous system Solvent in rubber, other organic products; chemical production wastes
Xylenes (total) 10 10 Liver, kidney, nervous system By-product of gasoline refining; paints, inks, detergents
Lead and Copper
Lead* zero TT+ Kidneys, nervous system damage Natural/industrial deposits; plumbing, solder, brass alloy faucets
Copper 1.3 TT# Gastrointestinal irritation Natural/industrial deposits; wood preservatives, plumbing
Other Standards
Beta/photon emitters zero 4mrem/yr Cancer Decay of radionuclides in natural and man-made deposits
Alpha emitters zero 15pCi/L Cancer Decay of radionuclides in natural deposits
Combined Radium 226/228 zero 5pCi/L Bone cancer Natural deposits
Arsenic* 0.010 0.010 Skin, nervous system toxicity Natural deposits; smelters, glass, electronics wastes; orchards
Total Trihalomethanes zero 0.10 Cancer Drinking water chlorination by-products
Notes: +=Action Level 0.015mg/L

#=Action Level 1.3 mg/L

*Contaminants with interim standards which have been revised.




1 Maximum Contaminant Level Goal (MCLG) - The maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health effect of persons would occur, and which allows for an adequate margin of safety. MCLGs are non-enforceable public health goals.

2 Maximum Contaminant Level (MCL) - The maximum permissible level of a contaminant in water which is delivered to any user of a public water system. MCLs are enforceable standards. The margins of safety in MCLGs ensure that exceeding the MCL slightly does not pose a significant risk to public health.

3 Treatment Technique - An enforceable procedure or level of technical performance which public water systems must follow to ensure control of a contaminant.

4 Units are in milligrams per Liter (mg/L) unless otherwise noted.

5 MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no MCLG for this contaminant.

6 Lead and copper are regulated in a Treatment Technique which requires systems to take tap water samples at sites with lead pipes or copper pipes that have lead solder and/or are served by lead service lines. The action level, which triggers water systems into taking treatment steps if exceeded in more than 10% of tap water samples, for copper is 1.3 mg/L, and for lead is 0.015mg/L.

7 Each water system must certify, in writing, to the state (using third-party or manufacturer's certification) that when acrylamide and epichlorohydrin are used in drinking water systems, the combination (or product) of dose and monomer level does not exceed the levels specified, as follows:

  • Acrylamide = 0.05% dosed at 1 mg/L (or equivalent)
  • Epichlorohydrin = 0.01% dosed at 20 mg/L (or equivalent)

8 The Surface Water Treatment Rule requires systems using surface water or ground water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water to meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels:

  • Giardia lamblia: 99.9% killed/inactivated
    Viruses: 99.99% killed/inactivated
  • Legionella: No limit, but EPA believes that if Giardia and viruses are inactivated, Legionella will also be controlled.
  • Turbidity: At no time can turbidity (cloudiness of water) go above 5 nephelometric turbidity units (NTU); systems that filter must ensure that the turbidity go no higher than 1 NTU (0.5 NTU for conventional or direct filtration) in at least 95% of the daily samples for any two consecutive months.
  • HPC: NO more than 500 bacterial colonies per milliliter.

9 No more than 5.0% samples total coliform-positive in a month. (For water systems that collect fewer than 40 routine samples per month, no more than one sample can be total coliform-positive). Every sample that has total coliforms must be analyzed for fecal coliforms. There cannot be any fecal coliforms.

10 Fecal coliform and E. coli are bacteria whose presence indicates that the water may be contaminated with human animal wastes. Microbes in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms.

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