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Water: Drinking Water Contaminants

On this Page

National Primary DW Regulations

List of DW Contaminants & MCLs

National Secondary DW Regs

List of Secondary DW Regulations

Unregulated Contaminants

Information on this section

Alphabetical List (PDF) (6 pp, 924 K)

(About PDF) EPA 816-F-09-0004,

May 2009

You are here: Water Drinking Water Drinking Water Contaminants

Drinking Water Contaminants

National Primary 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 public health by limiting the levels

of contaminants in drinking water. Visit the list of regulated

contaminants with links for more details.

List of Contaminants & their Maximum Contaminant Level (MCLs)

Regulation Development

EPA's Regulated Contaminant Timeline (PDF) (1 pp, 86 K ) (About PDF)

National Primary Drinking Water Regulations- The complete regulations regarding these contaminants

availible from the Code of Federal Regulations Website

List of Contaminants & their MCLs

An alphabetical listing with links to fact sheets on the primary drinking water regulations.

Microorganisms

Disinfectants

Disinfection Byproducts

Inorganic Chemicals

Organic Chemicals

Radionuclides

Microorganisms

Contaminant MCLG

1

(mg/L)

2

MCL or

TT

1

(mg/L)

2

Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as

short-term)

Sources of Contaminant in

Drinking Water

Cryptosporidium zero TT

3 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste

Giardia lamblia zero TT

3 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste

Heterotrophic

plate count

n/a TT

3 HPC has no health effects; it is an analytic method used to measure the variety of bacteria that

are common in water. The lower the concentration of bacteria in drinking water, the better

maintained the water system is.

HPC measures a range of

bacteria that are naturally

present in the environment

Legionella zero TT

3 Legionnaire's Disease, a type of pneumonia Found naturally in water;

multiplies in heating systems

Total Coliforms

(including fecal

coliform and E.

Coli)

zero 5.0%

4 Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may

be present

5

Coliforms are naturally present

in the environment; as well as

feces; fecal coliforms and E.

coli only come from human and

animal fecal waste.

Turbidity n/a TT

3 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 TT

3 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste

Disinfection Byproducts
water.epa.gov/drink/contaminants/index.cfm 2/7

Contaminant MCLG

1

(mg/L)

2

MCL or TT

1

(mg/L)

2

Potential Health Effects from Long-Term Exposure Above the MCL (unless

specified as short-term)

Sources of Contaminant in

Drinking Water

Bromate zero 0.010 Increased risk of cancer Byproduct of drinking water

disinfection

Chlorite 0.8 1.0 Anemia; infants & young children: nervous system effects Byproduct of drinking water

disinfection

Haloacetic acids

(HAA5)

n/a

6

0.060

7

Increased risk of cancer Byproduct of drinking water

disinfection

Total Trihalomethanes

(TTHMs)

--> n/a

6

--> 0.080

7 Liver, kidney or central nervous system problems; increased risk of cancer Byproduct of drinking water

disinfection

Disinfectants

Contaminant MCLG

1

(mg/L)

2

MCL or TT

1

(mg/L)

2

Potential Health Effects from Long-Term Exposure Above the MCL (unless

specified as short-term)

Sources of Contaminant in

Drinking Water

Chloramines (as

Cl2)

MRDLG=4

1 MRDL=4.01 Eye/nose irritation; stomach discomfort, anemia Water additive used to control

microbes

Chlorine (as Cl2) MRDLG=4

1 MRDL=4.01 Eye/nose irritation; stomach discomfort Water additive used to control

microbes

Chlorine dioxide (as

ClO2)

MRDLG=0.8

1 MRDL=0.81 Anemia; infants & young children: nervous system effects Water additive used to control

microbes

Inorganic Chemicals

Contaminant MCLG

1

(mg/L)

2

MCL or TT

1

(mg/L)

2

Potential Health Effects from Long-Term Exposure Above the MCL (unless

specified as short-term)

Sources of Contaminant in Drinking Water

Antimony 0.006 0.006 Increase in blood cholesterol; decrease in blood sugar Discharge from petroleum refineries; fire

retardants; ceramics; electronics; solder

Arsenic 0

7 0.010 as of

01/23/06

Skin damage or problems with circulatory systems, and may have increased

risk of getting cancer

Erosion of natural deposits; runoff from

orchards, runoff from glass &

electronicsproduction 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 coalburning 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 Allergic dermatitis Discharge from steel and pulp mills; erosion of

natural deposits

Copper 1.3 TT

7

; Action

Level=1.3

Short term exposure: Gastrointestinal distress

Long term exposure: Liver or kidney damage

Corrosion of household plumbing systems;

erosion of natural deposits
water.epa.gov/drink/contaminants/index.cfm 3/7

People with Wilson's Disease should consult their personal doctor if the

amount of copper in their water exceeds the action level

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 TT

7

; Action

Level=0.015

Infants and children: Delays in physical or mental development; children could

show slight deficits in attention span and learning abilities

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

croplands

Nitrate

(measured

as Nitrogen)

10 10 Infants below the age of six months who drink water containing nitrate in

excess of the MCL could become seriously ill and, if untreated, may die.

Symptoms include shortness of breath and blue-baby syndrome.

Runoff from fertilizer use; leaking from septic

tanks, sewage; erosion of natural deposits

Nitrite

(measured

as Nitrogen)

1 1 Infants below the age of six months who drink water containing nitrite in

excess of the MCL could become seriously ill and, if untreated, may die.

Symptoms include shortness of breath and blue-baby syndrome.

Runoff from fertilizer use; leaking 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 drug factories

Organic Chemicals

Contaminant MCLG

1

(mg/L)

2

MCL or TT

1

(mg/L)

2

Potential Health Effects from Long-Term Exposure Above the

MCL (unless specified as short-term)

Sources of Contaminant in Drinking Water

Acrylamide zero TT

8 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 or reproductive problems 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, nervous system, or reproductive system 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
water.epa.gov/drink/contaminants/index.cfm 4/7

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 drug 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 Weight loss, liver problems, or possible reproductive difficulties. 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 Liver problems Residue of banned insecticide

Epichlorohydrin zero TT

8

Increased cancer risk, and over a long period of time, stomach

problems

Discharge from industrial chemical factories;

an impurity of some water treatment chemicals

Ethylbenzene 0.7 0.7 Liver or kidneys problems Discharge from petroleum refineries

Ethylene dibromide zero 0.00005 Problems with liver, stomach, reproductive system, or kidneys;

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
water.epa.gov/drink/contaminants/index.cfm 5/7

Heptachlor epoxide zero 0.0002 Liver damage; increased risk of cancer Breakdown of heptachlor

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

cattle, 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 landfills; discharge of waste

chemicals

Pentachlorophenol zero 0.001 Liver or kidney problems; increased cancer risk 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, or circulatory system 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 metal degreasing sites and

other factories

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
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Radionuclides

Contaminant MCLG

1

(mg/L)

2

MCL or TT

1

(mg/L)

2

Potential Health Effects from Long-Term Exposure

Above the MCL (unless specified as short-term)

Sources of Contaminant in Drinking Water

Alpha particles none

7

--

--------

zero

15 picocuries

per Liter

(pCi/L)

Increased risk of cancer Erosion of natural deposits of certain minerals that are

radioactive and may emit a form of radiation known as alpha

radiation

Beta particles and

photon emitters

none

7

--

--------

zero

4 millirems

per year

Increased risk of cancer Decay of natural and man-made deposits of

certain minerals that are radioactive and may emit forms of

radiation known as photons and beta radiation

Radium 226 and

Radium 228

(combined)

none

7

--

--------

zero

5 pCi/L Increased risk of cancer Erosion of natural deposits

Uranium zero 30 ug/L as of

12/08/03

Increased risk of cancer, kidney toxicity Erosion of natural deposits

Notes

1 Definitions: 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 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 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. (TT) Treatment Technique - A required process intended to reduce the

level of a contaminant in drinking water. 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.

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: Unfiltered systems are required to include Cryptosporidium in their existing watershed control provisions.

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, according to the treatment techniques in the Surface Water Treatment

Rule, Legionella will also be controlled.

Turbidity: For systems that use conventional or direct filtration, at no time can turbidity (cloudiness of water) go higher than 1 nephelolometric turbidity unit NTU),

and samples for turbidity must be less than or equal to 0.3 NTU in at least 95 percent of the samples in any month. Systems that use filtration other than the

conventional or direct filtration must follow state limits, which must include turbidity at no time exceeding 5 NTU.

HPC: No more than 500 bacterial colonies per milliliter.

Long Term 1 Enhanced Surface Water Treatment: Surface water systems or (GWUDI) systems serving fewer than 10,000 people must comply with the applicable

Long Term 1 Enhanced Surface Water Treatment Rule provisions (e.g. turbidity standards, individual filter monitoring, Cryptosporidium removal requirements,

updated watershed control requirements for unfiltered systems).

Long Term 2 Enhanced Surface Water Treatment Rule This rule applies to all surface water systems or ground water systems under the direct influence of surface

water. The rule targets additional Cryptosporidium treatment requirements for higher risk systems and includes provisions to reduce risks from uncovered finished

water storage facilities and to ensure that the systems maintain microbial protection as they take steps to reduce the formation of disinfection byproducts.

Filter Backwash Recycling; The Filter Backwash Recycling Rule requires systems that recycle to return specific recycle flows through all processes of the

system's existing conventional or direct filtration system or at an alternate location approved by the state.

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 per month.) Every sample that has total coliform must be analyzed for either fecal coliforms or E. coli if two consecutive TC-positive samples, and

one is also positive for E.coli fecal coliforms, system has an acute MCL violation.

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 (0.07mg/L).

Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.02 mg/L); monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are

regulated with this group but have no MCLGs.

7 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.
water.epa.gov/drink/contaminants/index.cfm 7/7

Last updated on Tuesday, June 05, 2012

8 Each water system must certify, in writing, to the state (using third-party or manufacturer's certification) that when acrylamide and epichlorohydrin are used to treat water,

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.

National Secondary Drinking Water Regulations - The complete regulations regarding these contaminants available from the Code of Federal Regulations Web

Site.

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

List of National Secondary Drinking Water Regulations

Contaminant Secondary Standard

Aluminum 0.05 to 0.2 mg/L

Chloride 250 mg/L

Color 15 (color units)

Copper 1.0 mg/L

Corrosivity noncorrosive

Fluoride 2.0 mg/L

Foaming Agents 0.5 mg/L

Iron 0.3 mg/L

Manganese 0.05 mg/L

Odor 3 threshold odor number

pH 6.5-8.5

Silver 0.10 mg/L

Sulfate 250 mg/L

Total Dissolved Solids 500 mg/L

Zinc 5 mg/L

Unregulated Contaminants

This list of contaminants which, at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation (NPDWR), are known

or anticipated to occur in public water systems, and may require regulations under SDWA. For more information check out the list, or vist the Drinking Water Contaminant

Candidate List (CCL) web site.

Drinking Water Contaminant Candidate List 2

Drinking Water Contaminant Candidate List (CCL) Web Site

Unregulated Contaminant Monitoring Program (UCM)

Information on specific unregulated contaminants

MTBE (methyl-t-butyl ether) in drinking water