National Primary and Secondary Drinking Water Regulations

Mar 27th 2017

The US Environmental Protection Agency (EPA) sets Current Drinking Water Standards for drinking water. These standards are made up of the National Primary Drinking Water Regulations and the National Secondary Drinking Water Regulations. The Primary Standards set levels of contaminants that may pose a health risk when present in drinking water supplies and are known or anticipated to occur in public water systems. The Primary Standards contaminants are divided into Inorganic Chemicals, Organic Chemicals, Radionuclides and Microorganisms. The Secondary Standards are non enforceable guidelines that establish recommendations for contaminants that may cause cosmetic effects such as skin or tooth discoloration and aesthetic effects such as taste, odor and color. The EPA recommends Secondary Standards to water treatment systems but does not require systems to comply. The Safe Drinking Water Act (SDWA) was passed in 1974 and has been amended in 1986 and 1996. Despite strict and comprehensive government guidelines, our drinking water can contain contaminants that pose serious health risks.

The National Primary Drinking Water Standards establish a Maximum Contaminant Level (MCL) and a Maximum Contaminant Level Goal (MCLG) for certain water pollutants. The MCL is the maximum permissible level of a contaminant in drinking water which is delivered to any user in a public water system. These standards are established by considering contaminant impact on human health and what is technologically and economically feasible for removal by a treatment facility. The MCLG is the level of a contaminant at which there would be no risk to human health. This goal is not always technologically or economically feasible by a water treatment facility and is not enforceable.

If you have a well system for your home, you are responsible for your water quality and assuring it is safe for you and your family. Generally, homeowners only test their well water after the well system is installed and may not do it again. This initial test is usually a requirement for the local board of health and may not check for all the EPA Safe Water Drinking Act standards. Failure to check your water can be a dangerous gamble as ground and surface water is susceptible to contaminants at all times. Without a periodic comprehensive test of your drinking water, you may be putting yourself and your family at risk.

Primary Drinking Water Standards

Primary Drinking Water Regulations are legally enforceable standards that limit the level of specific contaminants that can adversely affect public health and are known or anticipated to occur in water. Units for the regulations are displayed in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million. These regulations take several forms:

  • Maximum Contaminant Level (MCL) - The maximum permissible level of a contaminant in water delivered to any user in a public water system. MCL's are set as close to MCLG's as is economically and technologically feasible. These 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. These MCLG's allow for a margin of Safety and are non-enforceable public health goals.
  • Treatment Technique (TT) - 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.
  • 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.

Microorganisms

Contaminant MCLG
(mg/L)
MCL or TT
(mg/L)
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Cryptosporidium zero
(see note 1)
Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and fecal animal waste
Giardia lamblia zero
(see note 1)
Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste
Heterotrophic plate count n/a
(see note 1)
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
(see note 1)
Legionnaire's Disease, a type of pneumonia Found naturally in water; multiplies in heating systems
Total Coliforms (including fecal coliform and E. Coli)
(see note 3)
zero
(see note 2)
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
(see note 1)
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
(see note 1)
Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste

Note 1 - 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 of 1/1/02 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.

Note 2 - 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.

Note 3 - 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.

Disinfection Byproducts

Contaminant

MCLG
(mg/L)
MCL or TT
(mg/L)
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/a
(see note 4)
0.060 Increased risk of cancer Byproduct of drinking water disinfection
Total Trihalomethanes (TTHMs)
none
(see note 5)
----------
n/a
(see note 4)
0.10
----------
0.080
Liver, kidney or central nervous system problems; increased risk of cancer Byproduct of drinking water disinfection

Note 4 - 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.

Note 5 - MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no MCLG for this contaminant.

Disinfection

Contaminant

MRDLG
(mg/L)
MRDL(mg/L) Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Chloramines (as Cl2) MRDLG = 4 MRDL = 4.0 Eye/nose irritation; stomach discomfort, anemia Water additive used to control microbes
Chlorine (as Cl2) MRDLG = 4 MRDL = 4.0 Eye/nose irritation; stomach discomfort Water additive used to control microbes
Chlorine dioxide (as ClO2) MRDLG = 0.8 MRDL = 0.8 Anemia; infants & young children: nervous system effects Water additive used to control microbes

Inorganic Chemicals

Contaminant MCLG
(mg/L)
MCL or TT
(mg/L)
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
(see note 5)
0.010 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 & electronics production wastes
Asbestos
(fiber >10 micrometers)
7 MFL
(see note 6)
7 MFL
(see note 6)
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
TT Action Level=1.3
(see note 7)
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
TT Action Level=0.015
(see note 7)
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 and plumbing fixtures such as faucets from lead solder and lead content; erosion of natural deposits (see note 8)
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

Note 5 - MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no MCLG for this contaminant.

Note 6 - MFL is million fibers per liter.

Note 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 or 15 parts per billion (ppb).

Note 8 - In 1986, the Safe Drinking Water Act (SWDA) amendment restricted the use of lead solder, flux and pipes in public water systems. In 1996, another amendment to the SWDA requires that all pipe, plumbing fittings and plumbing fixtures distributed after August 6, 1998 intended to disperse water for human consumption be "Lead Free". The term "Lead Free" does not mean it is "Free From Lead" as would be understood by the average consumer. "Lead Free" is defined in section 1417 of the Safe Water Drinking Act as:

  • Solders and Flux - may not contain more than 0.2% lead.
  • Pipes, Pipe Fittings, Well Pumps and Fixtures (faucets, drinking fountains, water dispensers, etc) - may not contain more than 8.0% lead.

The Maximum Contaminant Level Goal (MCLG) for Lead is zero. This is the level of a contaminant in drinking water below which there is no known or expected risk to health. Plumbing fixtures with 8% or less lead content can leach Lead into drinking water. A voluntary standard, NSF Standard 61, Section 9, for endpoint devices, has been established to verify compliance with the "Lead Free" rule. The NSF Standard is designed to limit Lead leaching from plumbing fixtures to 11 parts per billion (ppb). The Action Level for Lead under the National Drinking Water Standards is 15 ppb. The NSF Standard assumes other sources for Lead will not exceed 4 ppb. Since a Community Water Supplier is allowed to provide drinking water up to 15 ppb and be in compliance with the National Primary Drinking Water Standard, the combination of a faucet that can leach Lead up to 11 ppb and a supply water of 15 ppb, could provide water at a level of up to 26 ppb Lead and still meet all federal requirements and far exceed the Maximum Contaminant Level Goal for Lead of zero. Click here for more information on Lead in Plumbing Products.

Organic Chemicals

Contaminant

MCLG
(mg/L)
MCL or TT
(mg/L)
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Acrylamide zero
(see note 9)
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
(see note 9)
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

Note 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)

Radionuclides

Contaminant MCLG
(mg/L)
MCL or TT
(mg/L)
Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Alpha particles
none
(see note 5)

----------
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
(see note 5)

----------
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
(see note 5)

----------
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

Note 5 - MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no MCLG for this contaminant.

Secondary Drinking Water Regulations

National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-mandatory water quality standards for 15 contaminants. EPA does not enforce these "secondary maximum contaminant levels" or "SMCLs." They are established only as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color and odor. These contaminants are not considered to present a risk to human health at the SMCL's. Public water systems may test for these standards on a voluntary basis, however, states may choose to adopt them as enforceable standards.

The US EPA believes that if these contaminants are present in your water at levels above these standards, the contaminants may cause the water to appear cloudy or colored, or to taste or smell bad. This may cause a great number of people to stop using water from their public water system even though the water is actually safe to drink. Secondary standards are set to give public water systems some guidance on removing these chemicals to levels that are below what most people will find to be noticeable.

There are a wide variety of problems related to secondary contaminants. These problems can be grouped into three categories:

  • Aesthetic Effects - undesirable Tastes or Odors, Color and Foaming
  • Cosmetic Effects - effects which do not damage the body but are still undesirable such as Skin Discoloration, Tooth Discoloration & Pitting.
  • Technical Effects - damage to water equipment or reduced effectiveness of treatment for other contaminants including Corrosivity and Scaling & Sedimentation.