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Current Drinking Water Standards

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National Primary Drinking Water Regulations (NPDWRs or primary standards) are legally enforceable standards that apply to public water systems. Primary standards protect public health by limiting the levels of contaminants in drinking water. The table below divides these contaminants into:

Microorganisms ~ Disinfectants & Disinfection Byproducts
Inorganic Chemicals ~ Organic Chemicals ~ Radionuclides

For more information, see Setting Standards for Safe Drinking Water to learn about EPA's standard-setting process or look at a timeline that shows the order in which EPA regulated these contaminants. For copies of the complete regulations regarding these contaminants, follow these links to the National Primary Drinking Water Regulations and National Secondary Drinking Water Regulations.

National Primary Drinking Water Regulations

Microorganisms MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Cryptosporidium
as of 01/01/02:
zero
as of 01/01/02:
TT 3
 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste
Giardia lamblia
zero
TT3
 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste
Heterotrophic plate count
n/a
TT3
 HPC has no health effects, but can indicate how effective treatment is at controlling microorganisms. HPC measures a range of bacteria that are naturally present in the environment
Legionella
zero
TT3
 Legionnaire's Disease, commonly known as pneumonia Found naturally in water; multiplies in heating systems
Total Coliforms (including fecal coliform and E. Coli)
zero
5.0%4
 Used as an indicator that other potentially harmful bacteria may be present5 Coliforms are naturally present in the environment; fecal coliforms and E. coli come from human and animal fecal waste.
Turbidity
n/a
TT3
 Turbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (e.g., whether disease-causing organisms are present). Higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches. Soil runoff
Viruses (enteric)
zero
TT3
 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste

Disinfectants & Disinfection Byproducts MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Bromate
as of 01/01/02:
zero
as of 01/01/02:
0.010
 Increased risk of cancer Byproduct of drinking water disinfection
Chloramines (as Cl2)
as of 01/01/02:
MRDLG=41
as of 01/01/02:
MRDL=4.01
 Eye/nose irritation; stomach discomfort, anemia Water additive used to control microbes
Chlorine (as Cl2)
as of 01/01/02:
MRDLG=41
as of 01/01/02:
MRDL=4.01
 Eye/nose irritation; stomach discomfort Water additive used to control microbes
Chlorine dioxide (as ClO2)
as of 01/01/02:
MRDLG=0.81
as of 01/01/02:
MRDL=0.81
 Anemia;
infants & young children: nervous system effects		 Water additive used to control microbes
Chlorite
as of 01/01/02:
0.8
as of 01/01/02:
1.0
 Anemia;
infants & young children: nervous system effects		 Byproduct of drinking water disinfection
Haloacetic acids (HAA5)
as of 01/01/02:
n/a6
as of 01/01/02:
0.060
 Increased risk of cancer Byproduct of drinking water disinfection
Total Trihalomethanes (TTHMs)
none7
----------
as of 01/01/02:
n/a6
0.10
----------
as of 01/01/02:
0.080
 Liver, kidney or central nervous system problems; increased risk of cancer Byproduct of drinking water disinfection

Inorganic Chemicals MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Antimony
0.006
0.006
 Increase in blood cholesterol; decrease in blood glucose Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder
Arsenic
none7
0.05
 Skin damage; circulatory system problems; increased risk of cancer Erosion of natural deposits; runoff from glass & electronics production wastes
Asbestos
(fiber >10 micrometers)
7 million fibers per liter
7 MFL
 Increased risk of developing benign intestinal polyps Decay of asbestos cement in water mains; erosion of natural deposits
Barium
2
2
 Increase in blood pressure Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits
Beryllium
0.004
0.004
 Intestinal lesions Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries
Cadmium
0.005
0.005
 Kidney damage Corrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints
Chromium (total)
0.1
0.1
 Some people who use water containing chromium well in excess of the MCL over many years could experience allergic dermatitis Discharge from steel and pulp mills; erosion of natural deposits
Copper
1.3
TT8;
Action Level=1.3
 Short term exposure: Gastrointestinal distress.
Long term exposure: Liver or kidney damage. People 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
Cyanide (as free cyanide)
0.2
0.2
 Nerve damage or thyroid problems Discharge from steel/metal factories; discharge from plastic and fertilizer factories
Fluoride
4.0
4.0
 Bone 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
Lead
zero
TT8;
Action Level=0.015
 Infants and children: Delays in physical or mental development.
Adults: Kidney problems; high blood pressure		 Corrosion of household plumbing systems; erosion of natural deposits
Mercury (inorganic)
0.002
0.002
 Kidney damage Erosion of natural deposits; discharge from refineries and factories; runoff from landfills and cropland
Nitrate (measured as Nitrogen)
10
10
 "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)
1
1
 "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
Selenium
0.05
0.05
 Hair or fingernail loss; numbness in fingers or toes; circulatory problems Discharge from petroleum refineries; erosion of natural deposits; discharge from mines
Thallium
0.0005
0.002
 Hair loss; changes in blood; kidney, intestine, or liver problems Leaching from ore-processing sites; discharge from electronics, glass, and pharmaceutical companies

 
Organic
Chemicals		 MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Acrylamide
zero
TT9
 Nervous system or blood problems; increased risk of cancer Added to water during sewage/wastewater treatment
Alachlor
zero
0.002
 Eye, liver, kidney or spleen problems; anemia; increased risk of cancer Runoff from herbicide used on row crops
Atrazine
0.003
0.003
 Cardiovascular system problems; reproductive difficulties Runoff from herbicide used on row crops
Benzene
zero
0.005
 Anemia; decrease in blood platelets; increased risk of cancer Discharge from factories; leaching from gas storage tanks and landfills
Benzo(a)pyrene (PAHs)
zero
0.0002
 Reproductive difficulties; increased risk of cancer Leaching from linings of water storage tanks and distribution lines
Carbofuran
0.04
0.04
 Problems with blood or nervous system; reproductive difficulties. Leaching of soil fumigant used on rice and alfalfa
Carbon
tetrachloride
zero
0.005
 Liver problems; increased risk of cancer Discharge from chemical plants and other industrial activities
Chlordane
zero
0.002
 Liver or nervous system problems; increased risk of cancer Residue of banned termiticide
Chlorobenzene
0.1
0.1
 Liver or kidney problems Discharge from chemical and agricultural chemical factories
2,4-D
0.07
0.07
 Kidney, liver, or adrenal gland problems Runoff from herbicide used on row crops
Dalapon
0.2
0.2
 Minor kidney changes Runoff from herbicide used on rights of way
1,2-Dibromo-3-chloropropane (DBCP)
zero
0.0002
 Reproductive difficulties; increased risk of cancer Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards
o-Dichlorobenzene
0.6
0.6
 Liver, kidney, or circulatory system problems Discharge from industrial chemical factories
p-Dichlorobenzene
0.075
0.075
 Anemia; liver, kidney or spleen damage; changes in blood Discharge from industrial chemical factories
1,2-Dichloroethane
zero
0.005
 Increased risk of cancer Discharge from industrial chemical factories
1,1-Dichloroethylene
0.007
0.007
 Liver problems Discharge from industrial chemical factories
cis-1,2-Dichloroethylene
0.07
0.07
 Liver problems Discharge from industrial chemical factories
trans-1,2-Dichloroethylene
0.1
0.1
 Liver problems Discharge from industrial chemical factories
Dichloromethane
zero
0.005
 Liver problems; increased risk of cancer Discharge from pharmaceutical and chemical factories
1,2-Dichloropropane
zero
0.005
 Increased risk of cancer Discharge from industrial chemical factories
Di(2-ethylhexyl) adipate
0.4
0.4
 General toxic effects or reproductive difficulties Leaching from PVC plumbing systems; discharge from chemical factories
Di(2-ethylhexyl) phthalate
zero
0.006
 Reproductive difficulties; liver problems; increased risk of cancer Discharge from rubber and chemical factories
Dinoseb
0.007
0.007
 Reproductive difficulties Runoff from herbicide used on soybeans and vegetables
Dioxin (2,3,7,8-TCDD)
zero
0.00000003
 Reproductive difficulties; increased risk of cancer Emissions from waste incineration and other combustion; discharge from chemical factories
Diquat
0.02
0.02
 Cataracts Runoff from herbicide use
Endothall
0.1
0.1
 Stomach and intestinal problems Runoff from herbicide use
Endrin
0.002
0.002
 Nervous system effects Residue of banned insecticide
Epichlorohydrin
zero
TT9
 Stomach problems; reproductive difficulties; increased risk of cancer Discharge from industrial chemical factories; added to water during treatment process
Ethylbenzene
0.7
0.7
 Liver or kidney problems Discharge from petroleum refineries
Ethelyne dibromide
zero
0.00005
 Stomach problems; reproductive difficulties; increased risk of cancer Discharge from petroleum refineries
Glyphosate
0.7
0.7
 Kidney problems; reproductive difficulties Runoff from herbicide use
Heptachlor
zero
0.0004
 Liver damage; increased risk of cancer Residue of banned termiticide
Heptachlor epoxide
zero
0.0002
 Liver damage; increased risk of cancer Breakdown of hepatachlor
Hexachlorobenzene
zero
0.001
 Liver or kidney problems; reproductive difficulties; increased risk of cancer Discharge from metal refineries and agricultural chemical factories
Hexachlorocyclopentadiene
0.05
0.05
 Kidney or stomach problems Discharge from chemical factories
Lindane
0.0002
0.0002
 Liver or kidney problems Runoff/leaching from insecticide used on catttle, lumber, gardens
Methoxychlor
0.04
0.04
 Reproductive difficulties Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock
Oxamyl (Vydate)
0.2
0.2
 Slight nervous system effects Runoff/leaching from insecticide used on apples, potatoes, and tomatoes
Polychlorinated
biphenyls (PCBs)
zero
0.0005
 Skin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer Runoff from landfils; discharge of waste chemicals
Pentachlorophenol
zero
0.001
 Liver or kidney problems; increased risk of cancer Discharge from wood preserving factories
Picloram
0.5
0.5
 Liver problems Herbicide runoff
Simazine
0.004
0.004
 Problems with blood Herbicide runoff
Styrene
0.1
0.1
 Liver, kidney, and circulatory problems Discharge from rubber and plastic factories; leaching from landfills
Tetrachloroethylene
zero
0.005
 Liver problems; increased risk of cancer Discharge from factories and dry cleaners
Toluene
1
1
 Nervous system, kidney, or liver problems Discharge from petroleum factories
Toxaphene
zero
0.003
 Kidney, liver, or thyroid problems; increased risk of cancer Runoff/leaching from insecticide used on cotton and cattle
2,4,5-TP (Silvex)
0.05
0.05
 Liver problems Residue of banned herbicide
1,2,4-Trichlorobenzene
0.07
0.07
 Changes in adrenal glands Discharge from textile finishing factories
1,1,1-Trichloroethane
0.20
0.2
 Liver, nervous system, or circulatory problems Discharge from metal degreasing sites and other factories
1,1,2-Trichloroethane
0.003
0.005
 Liver, kidney, or immune system problems Discharge from industrial chemical factories
Trichloroethylene
zero
0.005
 Liver problems; increased risk of cancer Discharge from petroleum refineries
Vinyl chloride
zero
0.002
 Increased risk of cancer Leaching from PVC pipes; discharge from plastic factories
Xylenes (total)
10
10
 Nervous system damage Discharge from petroleum factories; discharge from chemical factories

Radionuclides MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Alpha particles
none7
----------
as of 12/08/03:
zero
15 picocuries per Liter (pCi/L)
 Increased risk of cancer Erosion of natural deposits
Beta particles and photon emitters
none7
----------
as of 12/08/03:
zero
4 millirems per year
 Increased risk of cancer Decay of natural and man-made deposits
Radium 226 and Radium 228 (combined)
none7
----------
as of 12/08/03:
zero
5 pCi/L
 Increased risk of cancer Erosion of natural deposits
Uranium
as of 12/08/03:
zero
as of 12/08/03:
30 ug/L
 Increased risk of cancer, kidney toxicity Erosion of natural deposits

Notes

1 Definitions:
Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.
Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.
Maximum Residual Disinfectant Level (MRDL) - The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.
Maximum Residual Disinfectant Level Goal (MRDLG) - The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.
Treatment Technique - A required process intended to reduce the level of a contaminant in drinking water.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.

3 EPA's surface water treatment rules require systems using surface water or ground water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels:

  • Cryptosporidium: (as of January 1, 2002) 99% removal/inactivation
  • Giardia lamblia: 99.9% removal/inactivation
  • Viruses: 99.99% removal/inactivation
  • Legionella: No limit, but EPA believes that if Giardia and viruses are removed/inactivated, Legionella will also be controlled.
  • Turbidity: 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. As of January 1, 2002, turbidity may never exceed 1 NTU, and must not exceed 0.3 NTU in 95% of daily samples in any month.
  • HPC: No more than 500 bacterial colonies per milliliter.

4 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 may not be any fecal coliforms or E. coli.

5 Fecal coliform and E. coli are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms. These pathogens may pose a special health risk for infants, young children, and people with severely compromised immune systems.

6 Although there is no collective MCLG for this contaminant group, there are individual MCLGs for some of the individual contaminants:

  • Trihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/L). Chloroform is regulated with this group but has no MCLG.
  • Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.3 mg/L). Monochloroacetic acid, bromoacetic acid, and dibromoacetic acid are regulated with this group but have no MCLGs.

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

8 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/L, and for lead is 0.015 mg/L.

9 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)

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. For more information, read Secondary Drinking Water Regulations: Guidance for Nuisance Chemicals.

Contaminant Secondary 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

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