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List of Drinking
Water Contaminants & MCLs
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. Vist the list of regulated contaminants with links
for more details.
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.
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) website.
List
of Contaminants & their MCLs |
EPA 816-F-02-013
July 2002
|
|
- The links provided below are to either Consumer Fact Sheet,
Rule Implementation websites, or PDF files
|
|
Microorganisms
Contaminant |
MCLG1
(mg/L)2 |
MCL or TT1
(mg/L)2 |
Potential Health
Effects from Ingestion of Water |
Sources of Contaminant
in Drinking Water |
Cryptosporidium |
zero
|
|
Gastrointestinal illness
(e.g., diarrhea, vomiting, cramps) |
Human and fecal animal
waste |
Giardia lamblia |
zero
|
|
Gastrointestinal illness
(e.g., diarrhea, vomiting, cramps) |
Human and animal fecal
waste |
Heterotrophic plate count |
n/a
|
|
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
|
|
Legionnaire's Disease,
a type of pneumonia |
Found naturally in water;
multiplies in heating systems |
Total Coliforms (including fecal
coliform and E. Coli) |
zero
|
|
Not a health threat in
itself; it is used to indicate whether other potentially harmful
bacteria may be present5 |
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
|
|
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
|
|
Gastrointestinal illness
(e.g., diarrhea, vomiting, cramps) |
Human and animal fecal
waste |
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) |
|
0.060
|
Increased risk of cancer |
Byproduct of drinking water disinfection |
Total Trihalomethanes
(TTHMs) |
|
0.10
----------
0.080
|
Liver, kidney or central nervous system
problems; increased risk of cancer |
Byproduct of drinking water disinfection |
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 |
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 |
|
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
|
|
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
|
|
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 |
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
|
|
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
|
|
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 |
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 |
|
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 |
|
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) |
|
5 pCi/L
|
Increased risk
of cancer |
Erosion of natural
deposits |
Uranium |
zero
|
|
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 of1/1/02 for systems serving >10,000 and 1/14/05
for systems serving <10,000) 99% removal.
- 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.
- Long Term 1 Enhanced Surface Water Treatment (Effective Date: January
14, 2005); 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).
- 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 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 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.
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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