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List of Contaminants & their MCLs


Microorganisms
Contaminant MCLG1
(mg/L)2
MCL or TT1
(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 (pdf file)
zero
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; 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
TT3

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
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

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Disinfection Byproducts
Contaminant MCLG1
(mg/L)2
MCL or TT1
(mg/L)2
Potential Health Effects from Ingestion of Water 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/a6
0.060

Increased risk of cancer

Byproduct of drinking water disinfection

Total Trihalomethanes (TTHMs)
n/a6
0.080

Liver, kidney or central nervous system problems; increased risk of cancer

Byproduct of drinking water disinfection

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Disinfectants
Contaminant MRDLG1
(mg/L)2
MRDL1
(mg/L)2
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Chloramines (as Cl2) MRDLG=41
MRDL=4.01

Eye/nose irritation; stomach discomfort, anemia

Water additive used to control microbes

Chlorine (as Cl2) MRDLG=41
MRDL=4.01

Eye/nose irritation; stomach discomfort

Water additive used to control microbes

Chlorine dioxide (as ClO2) MRDLG=0.81
MRDL=0.81

Anemia; infants & young children: nervous system effects

Water additive used to control microbes

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Inorganic Chemicals
Contaminant 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 sugar

Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder

Arsenic
07
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 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

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 the amount of copper in their water exceeds the 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; 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; leaching 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; 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 drug factories

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Organic Chemicals
Contaminant 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 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

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
TT9

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

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

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Radionuclides
Contaminant 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
----------
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
none7
----------
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)
none7
----------
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

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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.
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:

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:

7 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% percent 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 it is 0.015 mg/L.

8 Each water system must certify, in writing, to the state (using third-party or manufacturer's certification) that when it uses 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:

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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.

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


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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.

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