Water Experiments and Demonstrations National Primary Drinking Water Standards

Use the information in the table below to see how your community water system or well water quality compares to EPA standards.
Contaminant MCLG (mg/l) MCL (mg/l) Potential Health Effects Sources of Contaminant in Drinking Water
Bacteria, viruses, cloudiness        
Giardia lamblia zero TT Gastroenteric disease Human and animal fecal waste
Legionella N/A 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 water 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
Lead and Copper        
Lead* zero TT+ Kidney, nervous system damage Natural/industrial deposits; plumbing, solder, brass alloy faucets
Copper 1.3 TT# Gastrointestinal irritation Natural/industrial deposits; wood preservatives, plumbing
Antimony zero 0.006 Cancer Fire retardants, ceramics, electronics, fireworks, solder
Asbestos (>10µm) 7 MFL 7 MFL 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 system disorders Natural deposits; mining, electroplating, pigments
Cyanide 0.2 0.2 Thyroid, nervous system damage Electroplating, steel, plastics, mining, fertilizer
Fluoride 4.0 4.0 Skeletal and dental fluorosis Natural deposits; fertilizer, aluminum industries; water additive
Mercury* (inorganic) 0.002 0.002 Kidney, nervous system disorders Crop runoff; natural deposits; batteries, electrical switches
Nitrate* 10 10 Methemoglobulinemia Animal waste, fertilizer, natural deposits, septic tanks, sewage
Nitrite* 1 1 Methemoglobulinemia 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 effects Electronics, drugs, alloys, glass
Acrylamide zero TT Cancer, nervous systems effects Polymers used in sewage/waste water treatment
Adipate, (di(2-ethylhexyl)) 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 systems 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, kidney effects Herbicide on orchards, beans, coffee, lawns, roads, railways
Dibromochloropropane 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 and circulatory system effects Waste industrial extraction solvents
trans-1,2-Dichloroethylene 0.1 0.1 Liver, kidney, nervous and circulatory system effects 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
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 & aquatic weeds
2,4-D* 0.07 0.07 Liver and kidney damage Runoff of herbicide on wheat, corn, rangelands, lawns
Endothall 0.1 0.1 Liver, kidney, gastrointestinal effects 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 Waste treatment chemicals; waste epoxy resins, coatings
Ethylbenzene 0.7 0.7 Liver, kidney, nervous system effects 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
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 system effects Insecticide on cattle, lumber, gardens; restricted since 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
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; cancer Wood preservatives, herbicide, cooling tower wastes
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 and circulatory system effects Gasoline additive; manufacturing and solvent operations
Toxaphene zero 0.003 Cancer Insecticide on cattle, cotton, soybeans; cancelled 1982
2,4,5-TP 0.05 0.05 Liver and kidney damage Herbicide on crops, right-of-way, golf courses; cancelled 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 effects Solvent in rubber and other organic products; chemical production wastes
Xylenes (total) 10 10 Liver, kidney, nervous system effects By-product of gasoline refining; paints, inks, detergents
Volatile Organics        
Benzene zero 0.005 Cancer Some foods; gasoline, drugs, pesticides, paints, plastic industries
Carbon Tetrachloride zero 0.005 Cancer Solvents and their degradation products
p-Dichlorobenzene 0.075 0.075 Cancer Room and water deodorants, "mothballs"
1,2-Dichloroethane zero 0.005 Cancer Leaded gas, fumigants, paints
1,1-Dichloroethylene 0.007 0.007 Cancer Plastics, dyes, perfumes, paints
Trichloroethylene zero 0.005 Cancer Textiles, adhesives, 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 break down
Other Interim Standards        
Beta/photon emitters zero 4 mrem/yr Cancer Decay of radionuclides in natural and man-made deposits
Alpha emitters zero 15 pCi/L Cancer Decay of radionuclides in natural deposits
Radium 226/228
zero 5 pCi/L Bone cancer Natural deposits
Arsenic* 0.05 0.05 Skin, nervous system toxicity Natural deposits; smelters, glass, electronics wastes; orchards
Total Trihalomethanes zero 0.10 Cancer Drinking water chlorination by-products
Source: EPA, "Water on Tap," July 1997.

Notes: *Contaminants with interim standards which have been revised.
TT=Special treatment techniques required.
+=Action Level 0.015 mg/L.
#=Action Level 1.2 mg/L.

The Safe Drinking Water Act requires EPA to identify pollutants in drinking water that may adversely affect human health. These are listed in the table above. Where feasible, the agency is required to specify a Maximum Contaminant Level (MCL) for each pollutant. These MCLs are referred to as the National Primary Drinking Water Standards (NPDWS). Some of the contaminants listed above do not have established MCLs because it is not possible to determine their levels in drinking water. For these substances, EPA requires the use of specific treatment techniques (depending on the contaminant), identified by the initials "TT" in the MCL column.

Public water systems are required to meet these standards.

The MCLs for the listed contaminants are set as close to the Maximum Contaminant Level Goal (MCLG) as cost-effective treatment technologies allow. The MCLGs are almost entirely a health-based determination (for example, the MCLG for substances suspected to cause cancer is zero).

Note: Individual states may enforce their own drinking water standards as long as they are no less stringent than the NPDWS regulations. Each state may regulate additional contaminants in drinking water or may establish more stringent MCLs for the contaminants listed in the table above. For a list of the drinking water contaminants regulated by your state, contact your state agency. EPA has a list on the
Safe Drinking Water Hotline at (800) 426-4791

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