Current Drinking Water Standards

National Primary and Secondary Drinking Water Regulations

National Primary Drinking Water Regulations (NPDWRs or primary standards) are legally enforceable standards that apply to public water systems. Primary standards protect drinking water quality by limiting the levels of specific contaminants that can adversely affect public health and are known or anticipated to occur in public water systems. Table 1 divides these contaminants into Inorganic Chemicals, Organic Chemicals, Radionuclides, and Microorganisms. See Setting Standards for Safe Drinking Water to learn about EPA's standard-setting process. Follow these links to download copies of National Primary Drinking Water Regulations and National Secondary Drinking Water Regulations.

 

National Primary Drinking Water Regulations

ContaminantsMCLG1
(mg/L)4
MCL2 or TT3
(mg/L)4
Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
Inorganic Chemicals
Antimony0.0060.006Increase in blood cholesterol; decrease in blood glucoseDischarge from petroleum refineries; fire retardants; ceramics; electronics; solder 
Arsenicnone50.05Skin damage; circulatory system problems; increased risk of cancerDischarge from semiconductor manufacturing; petroleum refining; wood preservatives; animal feed additives; herbicides; erosion of natural deposits 
Asbestos
(fiber >10 micrometers)
7 million fibers per Liter7 MFLIncreased risk of developing benign intestinal polypsDecay of asbestos cement in water mains; erosion of natural deposits 
Barium22Increase in blood pressureDischarge of drilling wastes; discharge from metal refineries; erosion of natural deposits 
Beryllium0.0040.004Intestinal lesionsDischarge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries 
Cadmium0.0050.005Kidney damageCorrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints 
Chromium (total)0.10.1Some people who use water containing chromium well in excess of the MCL over many years could experience allergic dermatitisDischarge from steel and pulp mills; erosion of natural deposits 
Copper1.3Action Level=1.3; TT6Short term exposure: Gastrointestinal distress.
Long term exposure: Liver or kidney damage. Those with Wilson's Disease should consult their personal doctor if their water systems exceed the copper action level.
 Corrosion of household plumbing systems; erosion of natural deposits; leaching from wood preservatives 
Cyanide (as free cyanide)0.20.2Nerve damage or thyroid problemsDischarge from steel/metal factories; discharge from plastic and fertilizer factories 
Fluoride4.04.0Bone disease (pain and tenderness of the bones); Children may get mottled teeth.Water additive which promotes strong teeth; erosion of natural deposits; discharge from fertilizer and aluminum factories 
LeadzeroAction Level=0.015; TT6Infants and children: Delays in physical or mental development.
Adults: Kidney problems; high blood pressure
Corrosion of household plumbing systems; erosion of natural deposits 
Inorganic Mercury0.0020.002Kidney damageErosion of natural deposits; discharge from refineries and factories; runoff from landfills and cropland 
Nitrate (measured as Nitrogen)1010"Blue baby syndrome" in infants under six months - life threatening without immediate medical attention.
Symptoms: Infant looks blue and has shortness of breath.
Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits 
Nitrite (measured as Nitrogen)11"Blue baby syndrome" in infants under six months - life threatening without immediate medical attention.
Symptoms: Infant looks blue and has shortness of breath.
Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits 
 
Selenium0.050.05Hair or fingernail loss; numbness in fingers or toes; circulatory problemsDischarge from petroleum refineries; erosion of natural deposits; discharge from mines  
Thallium0.00050.002Hair loss; changes in blood; kidney, intestine, or liver problemsLeaching from ore-processing sites; discharge from electronics, glass, and pharmaceutical companies
Organic ChemicalsMCLG1
(mg/L)4
MCL2 or TT3
(mg/L)4
Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
 
AcrylamidezeroTT7Nervous system or blood problems; increased risk of cancerAdded to water during sewage/wastewater treatment 
Alachlorzero0.002Eye, liver, kidney or spleen problems; anemia; increased risk of cancerRunoff from herbicide used on row crops
Atrazine0.0030.003Cardiovascular system problems; reproductive difficultiesRunoff from herbicide used on row crops
Benzenezero0.005Anemia; decrease in blood platelets; increased risk of cancerDischarge from factories; leaching from gas storage tanks and landfills
Benzo(a)pyrenezero0.0002Reproductive difficulties; increased risk of cancerLeaching from linings of water storage tanks and distribution lines
Carbofuran0.040.04Problems with blood or nervous system; reproductive difficulties.Leaching of soil fumigant used on rice and alfalfa
Carbon tetrachloridezero.005Liver problems; increased risk of cancerDischarge from chemical plants and other industrial activities
Chlordanezero0.002Liver or nervous system problems; increased risk of cancerResidue of banned termiticide
Chlorobenzene0.10.1Liver or kidney problemsDischarger from chemical and agricultural chemical factories
2,4-D0.070.07Kidney, liver, or adrenal gland problemsRunoff from herbicide used on row crops
Dalapon0.20.2Minor kidney changesRunoff from herbicide used on rights of way
1,2-Dibromo-3-chloropropane (DBCP)zero0.0002Reproductive difficulties; increased risk of cancerRunoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards
o-Dichlorobenzene0.60.6Liver, kidney, or circulatory system problemsDischarge from industrial chemical factories
p-Dichlorobenzene0.0750.075Anemia; liver, kidney or spleen damage; changes in bloodDischarge from industrial chemical factories
1,2-Dichloroethanezero0.005Increased risk of cancerDischarge from industrial chemical factories
1-1-Dichloroethylene0.0070.007Liver problemsDischarge from industrial chemical factories
cis-1, 2-Dichloroethylene0.070.07Liver problemsDischarge from industrial chemical factories
trans-1,2-Dichloroethylene0.10.1Liver problemsDischarge from industrial chemical factories
Dichloromethanezero0.005Liver problems; increased risk of cancerDischarge from pharmaceutical and chemical factories
1-2-Dichloropropanezero0.005Increased risk of cancerDischarge from industrial chemical factories
Di(2-ethylhexyl)adipate0.40.4General toxic effects or reproductive difficultiesLeaching from PVC plumbing systems; discharge from chemical factories
Di(2-ethylhexyl)phthalatezero0.006Reproductive difficulties; liver problems; increased risk of cancerDischarge from rubber and chemical factories
Dinoseb0.0070.007Reproductive difficultiesRunoff from herbicide used on soybeans and vegetables
Dioxin (2,3,7,8-TCDD)zero0.00000003Reproductive difficulties; increased risk of cancerEmissions from waste incineration and other combustion; discharge from chemical factories
Diquat0.020.02CataractsRunoff from herbicide use
Endothall0.10.1Stomach and intestinal problemsRunoff from herbicide use
Endrin0.0020.002Nervous system effectsResidue of banned insecticide
EpichlorohydrinzeroTT7Stomach problems; reproductive difficulties; increased risk of cancerDischarge from industrial chemical factories; added to water during treatment process
Ethylbenzene0.70.7Liver or kidney problemsDischarge from petroleum refineries
Ethelyne dibromidezero0.00005Stomach problems; reproductive difficulties; increased risk of cancerDischarge from petroleum refineries
Glyphosate0.70.7Kidney problems; reproductive difficultiesRunoff from herbicide use
Heptachlorzero0.0004Liver damage; increased risk of cancerResidue of banned termiticide
Heptachlor epoxidezero0.0002Liver damage; increased risk of cancerBreakdown of hepatachlor
Hexachlorobenzenezero0.001Liver or kidney problems; reproductive difficulties; increased risk of cancerDischarge from metal refineries and agricultural chemical factories
Hexachlorocyclopentadiene0.050.05Kidney or stomach problemsDischarge from chemical factories
Lindane0.00020.0002Liver or kidney problemsRunoff/leaching from insecticide used on catttle, lumber, gardens
Methoxychlor0.040.04Reproductive difficultiesRunoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock
Oxamyl (Vydate)0.20.2Slight nervous system effectsRunoff/leaching from insecticide used on apples, potatoes, and tomatoes
Polychlorinated biphenyls (PCBs)zero0.0005Skin changes; thymus gland problems; immune difficiencies; reproductive or nervous system difficulties; increased risk of cancerRunoff from landfils; discharge of waste chemicals
Pentachlorophenolzero0.001Liver or kidney problems; increased risk of cancerDischarge from wood preserving factories
Picloram0.50.5Liver problemsHerbicide runoff
Simazine0.0040.004Problems with bloodHerbicide runoff
Styrene0.10.1Liver, kidney, and circulatory problemsDischarge from rubber and plastic factories; leaching from landfills
Tetrachloroethylenezero0.005Liver problems; increased risk of cancerDischarge from factories and dry cleaners
Toluene11Nervous system, kidney, or liver problemsDischarge from petroleum factories
Total Trihalomethanes (TTHMs)none50.10Liver, kidney or central nervous system problems; increased risk of cancerByproduct of drinking water disinfection
Toxaphenezero0.003Kidney, liver, or thyroid problems; increased risk of cancerRunoff/leaching from insecticide used on cotton and cattle
2,4,5-TP (Silvex)0.050.05Liver problemsResidue of banned herbicide
1,2,4-Trichlorobenzene0.070.07Changes in adrenal glandsDischarge from textile finishing factories
1,1,1-Trichloroethane0.200.2Liver, nervous system, or circulatory problemsDischarge from metal degreasing sites and other factories
1,1,2-Trichloroethane0.0030.005Liver, kidney, or immune system problemsDischarge from industrial chemical factories
Trichloroethylenezero0.005Liver problems; increased risk of cancerDischarge from petroleum refineries
Vinyl chloridezero0.002Increased risk of cancerLeaching from PVC pipes; discharge from plastic factories
Xylenes (total)1010Nervous system damageDischarge from petroleum factories; discharge from chemical factories
RadionuclidesMCLG1
(mg/L)4
MCL2 or TT3
(mg/L)4
Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
 
Beta particles and photon emittersnone54 millirems per yearIncreased risk of cancerDecay of natural and man-made deposits
Gross alpha particle activitynone515 picocuries per Liter (pCi/L)Increased risk of cancerErosion of natural deposits
Radium 226 and Radium 228 (combined)none55 pCi/LIncreased risk of cancerErosion of natural deposits
MicroorganismsMCLG1
(mg/L)4
MCL2 or TT3
(mg/L)4
Potential Health Effects from Ingestion of WaterSources of Contaminant in Drinking Water
 
Giardia lambliazeroTT8Giardiasis, a gastroenteric diseaseHuman and animal fecal waste
Heterotrophic plate countN/ATT8HPC has no health effects, but can indicate how effective treatment is at controlling microorganisms.n/a
LegionellazeroTT8Legionnaire's Disease, commonly known as pneumoniaFound naturally in water; multiplies in heating systems
Total Coliforms (including fecal coliform and E. Coli)zero5.0%9Used as an indicator that other potentially harmful bacteria may be present10Human and animal fecal waste
TurbidityN/ATT8Turbidity has no health effects but can interfere with disinfection and provide a medium for microbial growth. It may indicate the presence of microbes.Soil runoff
Viruses (enteric)zeroTT8Gastroenteric diseaseHuman and animal fecal waste
Table 1

 

National Secondary Drinking Water Regulations

National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards. See Table 2.

 

 
ContaminantSecondary Standard
Aluminum0.05 to 0.2 mg/L
Chloride250 mg/L
Color15 (color units)
Copper1.0 mg/L
Corrosivitynoncorrosive
Fluoride2.0 mg/L
Foaming Agents0.5 mg/L
Iron0.3 mg/L
Manganese0.05 mg/L
Odor3 threshold odor number
pH6.5-8.5
Silver0.10 mg/L
Sulfate250 mg/L
Total Dissolved Solids500 mg/L
Zinc5 mg/L
Table 2

Notes

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 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:

  bulletAcrylamide = 0.05% dosed at 1 mg/L (or equivalent)
bulletEpichlorohydrin = 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:

  bulletGiardia lamblia: 99.9% killed/inactivated
Viruses: 99.99% killed/inactivated
bulletLegionella: No limit, but EPA believes that if Giardia and viruses are inactivated, Legionella will also be controlled.
bulletTurbidity: At no time can turbidity (cloudiness of water) go above 5 nephelolometric 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 in any month.
bulletHPC: 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 witih human animal wastes. Microbes in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms.

 

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This page was updated on 23-Mar-2017

 

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