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

 

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 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 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 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 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 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 par