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Drinking Water Contaminants
You are here: EPA Home Water Safewater Drinking Water Contaminants
List of Contaminants & their MCLs
Microorganisms Disinfectants Disinfection Byproducts Inorganic Chemicals Organic Chemicals Radionuclides
Information on this section
Alphabetical List (PDF)
(6 pp, 924 K) (About PDF)
EPA 816-F-09-0004, May 2009
Microorganisms
Contaminant
MCLG1 (mg/L)
2
MCL or n-i
(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 (pdf file)
Gastrointestinal illness (e.g., Human and animal diarrhea, vomiting, cramps) fecal waste
Giardia lamblia
zero
Gastrointestinal illness (e.g., Human and animal diarrhea, vomiting, cramps) fecal waste
Heterotrophic plate count
n/a TT2
HPC has no health effects; it is HPC measures a
an analytic method used to
range of bacteria
measure the variety of
that are naturally
bacteria that are common in present in the
water. The lower the
environment
concentration of bacteria in
drinking water, the better
maintained the water system
is.
Legionella
zero
tt^
Legionnaire's Disease, a type Found naturally in
of pneumonia
water; multiplies in
heating systems
Total Conforms (including fecal
zero 5.0%Not a health threat in itself; it Coliforms are is used to indicate whether naturally present in
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coliform and E. Coli\
Turbidity
n/a
Viruses (enteric) zero
other potentially harmful bacteria may be present^
the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste.
j-pi
Turbidity is a measure of the Soil runoff 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.
jj3 Gastrointestinal illness (e.g., Human and animal diarrhea, vomiting, cramps) fecal waste
Disinfection Byproducts
Contaminant
MCLG1 (mg/L)
2
MCL or
tt!
(mg/L)
2
Potential Health Effects from Ingestion of Water
Bromate
zero 0.010 Increased risk of cancer
Sources of Contaminant in Drinking Water
Byproduct of drinking water disinfection
Chlorite
0.8 1.0
Anemia; infants & young children: nervous system effects
Byproduct of drinking water disinfection
Haloacetic acids n/a 0.060
(HAA5)
Increased risk of cancer
Byproduct of drinking water disinfection
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Iota] Trihalomethanes fTTHMsl
n/afi
0.080
Liver, kidney or central nervous system problems; increased risk of cancer
Byproduct of drinking water disinfection
Disinfectants Contaminant MRDLG1
(mg/L)2 Chloramines MPDLG--11 fas CIU
MRDL1 (mg/L)2
Potential Health Effects from
Ingestion of Water
MRDL=4.0i Eye/nose irritation;
stomach discomfort, anemia
Sources of Contaminant in Drinking Water
Water additive used to control microbes
Chlorine fas
Chi
MRDLG=4i
MRDL=4.01 Eye/nose irritation;
stomach discomfort
Water additive used to control microbes
Chlorine dioxide fas CIOU
MRDLG^O.81 MRDL=0.81
Anemia; infants &
Water additive used to
young children: nervous control microbes
system effects
Inorganic Chemicals
MCLG1 Contaminant (mg/L)
MCL or TT1
Potential Health Effects from Ingestion
2 (mg/L)2
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
02 0.010
as of
Skin damage or problems Erosion of natural
01/23/06 with circulatory systems, deposits; runoff from
and may have increased orchards, runoff from
risk of getting cancer
glass &
electronicsproduction
wastes
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Asbestos (fiber >10 micrometers')
7
million fibers per liter
7MFL
Increased risk of developing benign intestinal polyps
Decay of asbestos cement in water mains; erosion of natural deposits
Barium
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
0.1
0.1 Allergic dermatitis
Discharge from steel and pulp mills; erosion of natural deposits
Copper
1.3 jjS.
Action Short term exposure:
Corrosion of household
Level=1.3 Gastrointestinal distress plumbing systems;
erosion of natural
Long term exposure:
deposits
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
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Cyanide fas free cyanide1)
0.2
0.2
Nerve damage or thyroid Discharge from
problems
steel/metal factories;
discharge from plastic
and fertilizer factories
Fluoride
4.0 4.0
Bone disease (pain and Water additive which
tenderness of the
promotes strong teeth;
bones); Children may get erosion of natural
mottled teeth
deposits; discharge from
fertilizer and aluminum
factories
Lead
zero TT8;
Action Infants and children:
Corrosion of household
Level=0.015 Delays in physical or
plumbing systems;
mental development;
erosion of natural
children could show slight deposits
deficits in attention span
and learning abilities
Adults: Kidney problems; high blood pressure
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 Runoff from fertilizer
six months who drink
use; leaching from septic
water containing nitrate tanks, sewage; erosion
in excess of the MCL
of natural deposits
could become seriously ill
and, if untreated, may
die. Symptoms include
shortness of breath and
blue-baby syndrome.
Nitrite (measured as
Nitrogen)
1
1
Infants below the age of Runoff from fertilizer
six months who drink
use; leaching from septic
water containing nitrite in
excess of the MCL could
become seriously ill and,
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Selenium Thallium
0.05 0.0005
if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.
tanks, sewage; erosion of natural deposits
0.05
Hair or fingernail loss; Discharge from
numbness in fingers or petroleum refineries;
toes; circulatory
erosion of natural
problems
deposits; discharge from
mines
0.002
Hair loss; changes in blood; kidney, intestine, or liver problems
Leaching from oreprocessing sites; discharge from electronics, glass, and drug factories
Organic Chemicals Contaminant
Acrylamide
Alachlor
Atrazine
Benzene
MCLG1 (mg/L)
2
zero
MCL or TT1
(mg/L)2
TT2
Potential Health Effects from
Ingestion of Water
Sources of Contaminant in Drinking Water
Nervous system or Added to water
blood problems; during
increased risk of sewage/wastewater
cancer
treatment
zero 0.002
Eye, liver, kidney Runoff from
or spleen
herbicide used on
problems; anemia; row crops
increased risk of
cancer
0.003
0.003
Cardiovascular system or reproductive problems
Runoff from herbicide used on row crops
zero 0.005 Anemia; decrease Discharge from in blood platelets; factories; leaching
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Benzofalpvrene fPAHsl
Carbofuran
Carbon tetrachloride Chlordane
Chlorobenzene
2.4-D Dalapon 1.2-Dibromo-3chloropropane (DBCPi
zero 0.04
zero zero 0.1 0.07 0.2 zero
increased risk of from gas storage
cancer
tanks and landfills
0.0002
Reproductive difficulties; increased risk of cancer
Leaching from linings of water storage tanks and distribution lines
0.04
Problems with blood, nervous system, or reproductive system
Leaching of soil fumigant used on rice and alfalfa
0.005
Liver problems; increased risk of cancer
Discharge from chemical plants and other industrial activities
0.002
Liver or nervous system problems; increased risk of cancer
Residue of banned termiticide
0.1
Liver or kidney
Discharge from
problems
chemical and
agricultural
chemical factories
0.07
Kidney, liver, or Runoff from
adrenal gland
herbicide used on
problems
row crops
0.2 Minor kidney changes
Runoff from herbicide used on rights of way
0.0002
Reproductive difficulties;
Runoff/leaching from soil fumigant
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o-Dichlorobenzene
0.6
D-Dichlorobenzene
0.075
1.2-Dichloroethane
zero
1.1-Dichloroethvlene
0.007
cis-1.2-Dichloroethvlene
0.07
trans-1.2-Dichloroethvlene 0.1
Dichloromethane
zero
1.2-DichloroDroDane
zero
increased risk of cancer
used on soybeans, cotton, pineapples, and orchards
0.6
Liver, kidney, or Discharge from
circulatory system industrial chemical
problems
factories
0.075
Anemia; liver, kidney or spleen damage; changes in blood
Discharge from industrial chemical factories
0.005
Increased risk of cancer
Discharge from industrial chemical factories
0.007
Liver problems
Discharge from industrial chemical factories
0.07 Liver problems
Discharge from industrial chemical factories
0.1
Liver problems
Discharge from
industrial chemical
factories
0.005
Liver problems; increased risk of cancer
Discharge from drug and chemical factories
0.005
Increased risk of cancer
Discharge from industrial chemical factories
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Di(2-ethylhexyl) adipate
0.4
0.4
Weight loss, liver Discharge from
problems, or
chemical factories
possible
reproductive
difficulties.
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'i
zero 0.00000003
Reproductive difficulties; increased risk of cancer
Emissions from waste incineration and other combustion; discharge from chemical factories
Diauat
0.02
0.02 Cataracts
Runoff from herbicide use
Endothall
0.1 0.1
Stomach and
Runoff from
intestinal problems herbicide use
Endrin
0.002
0.002
Liver problems
Residue of banned insecticide
EDichlorohydrin
zero TT2 Increased cancer Discharge from
risk, and over a industrial chemical
long period of
factories; an
time, stomach
impurity of some
problems
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water treatment chemicals
Ethylbenzene
0.7 0.7
Liver or kidneys problems
Discharge from petroleum refineries
Ethvlene dibromide
zero 0.00005
Problems with
Discharge from
liver, stomach,
petroleum
reproductive system, or
refineries
kidneys; increased
risk of cancer
Glvphosate
0.7 0.7
Kidney problems; Runoff from
reproductive
herbicide use
difficulties
Heptachlor
zero 0.0004
Liver damage;
Residue of banned
increased risk of termiticide cancer
Heptachlor epoxide
zero 0.0002
Liver damage;
Breakdown of
increased risk of heptachlor
cancer
Hexachloro benzene
zero 0.001
Liver or kidney
Discharge from
problems;
metal refineries
reproductive
and agricultural
difficulties;
chemical factories
increased risk of
cancer
Hexachlorocvclopentadiene 0.05
0.05
Kidney or stomach Discharge from
problems
chemical factories
Lindane
0.0002
0.0002
Liver or kidney problems
Runoff/leaching from insecticide
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Methoxvchlor
Oxamvl fVvdatel
Polychlorinated biDhenvIs CPCBsl
PentachloroDhenol Picloram Simazine Stvrene
0.04 0.2 zero
zero 0.5 0.004 0.1
used on cattle, lumber, gardens
0.04
Reproductive difficulties
Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock
0.2
Slight nervous
Runoff/leaching
system effects
from insecticide
used on apples,
potatoes, and
tomatoes
0.0005
Skin changes;
Runoff from
thymus gland
landfills; discharge
problems; immune of waste chemicals
deficiencies;
reproductive or
nervous system
difficulties;
increased risk of
cancer
0.001
Liver or kidney problems; increased cancer risk
Discharge from wood preserving factories
0.5
Liver problems
Herbicide runoff
0.004
Problems with blood
Herbicide runoff
0.1
Liver, kidney, or Discharge from
circulatory system rubber and plastic
problems
factories; leaching
from landfills
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Tetrachloroethvlene Toluene Toxaphene 2.4.5-TP fSilvext 1.2.4-Trichlorobenzene 1.1.1-Trichloroethane 1.1.2-Trichloroethane Trichloroethylene Vinvl chloride
zero 1
zero 0.05 0.07 0.20 0.003 zero zero
0.005
Liver problems; increased risk of cancer
Discharge from factories and dry cleaners
1
Nervous system, Discharge from
kidney, or liver
petroleum factories
problems
0.003
Kidney, liver, or thyroid problems; increased risk of cancer
Runoff/leaching from insecticide used on cotton and cattle
0.05
Liver problems
Residue of banned herbicide
0.07
Changes in adrenal glands
Discharge from textile finishing factories
0.2
Liver, nervous
Discharge from
system, or
metal degreasing
circulatory
sites and other
problems
factories
0.005
Liver, kidney, or immune system problems
Discharge from industrial chemical factories
0.005
Liver problems; increased risk of cancer
Discharge from metal degreasing sites and other factories
0.002
Increased risk of Leaching from PVC
cancer
pipes; discharge
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Xylenes ftotall
from plastic factories
10 10
Nervous system Discharge from
damage
petroleum
factories; discharge
from chemical
factories
Radionuclides Contaminant
Alpha particles
MCLG1 MCL or
(mg/L) TT1 2 (mg/L)2
Potential Health Effects from Ingestion of Water
none2 zero
15 picocuries Increased risk of cancer per Liter
(pCi/L)
Sources of Contaminant in Drinking Water
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
none2
4
------------ millirems increased risk of cancer
zer0 per year
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)
none2 zero
5 pCi/L Increased risk of cancer
Erosion of natural deposits
Uranium
zero Increased risk of cancer, 30 ug/L kidney toxicity
as of
12/08/03
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:
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 not 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 pervent 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.
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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 conforms or E. coli if two consecutive TC-positive samples, and one is also positive for E.coli fecal conforms, 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). Flaloacetic 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% 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:
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 nonenforceable 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.
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List of National Secondary Drinking Water Regulations http://www.epa.g0v/safewater/c0ntaminants/index.html#sec
Contaminant
Last updated on Friday, Septembei Secondary Standard
Aluminum Chloride Color Copper Corrosivity Fluoride Foaming Agents Iron Manganese Odor pH Silver Sulfate Total Dissolved Solids Zinc
0.05 to 0.2 mg/L 250 mg/L
15 (color units) 1.0 mg/L
noncorrosive 2.0 mg/L 0.5 mg/L 0.3 mg/L
0.05 mg/L 3 threshold odor number
6.5-8.5 0.10 mg/L 250 mg/L 500 mg/L
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 fCCLj Web Site Unregulated Contaminant Monitoring Program (UCM1 Information on specific unregulated contaminants
MTBE (methyl-t-butyl ether) in drinking water
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