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National
Primary Drinking Water Regulations

List of
Drinking Water Contaminants & their MCLs

National
Secondary Drinking Water Regulations

List of
Secondary Drinking Water Regulations

Unregulated
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)

Setting
Standards for Safe Drinking Water to learn about EPA's standard-setting
process

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

Information on this section

Alphabetical
List (PDF)
(6 pp, 396 K) (About
PDF)
EPA 816-F-03-016, June 2003

The links provided below are to either Consumer Fact Sheet, Rule
Implementation web sites, or PDF files.
(About
PDF)

List of Contaminants
& their MCLs

Microorganisms

Disinfectants

Disinfection
Byproducts

Inorganic
Chemicals

Organic
Chemicals

Radionuclides

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
(pdf file)

zero

TT 3

Gastrointestinal illness (e.g., diarrhea, vomiting, cramps)

Human and fecal animal 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 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

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)

none7
----------
n/a6

0.10
----------
0.080

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

Byproduct of drinking water disinfection

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page

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 (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)

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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.

National
Secondary Drinking Water Regulations - The complete
regulations regarding these contaminants availible 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

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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.

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

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