The National Primary Drinking Water Regulations (NPDWR) is a set of standards established by the Environmental Protection Agency (EPA) in the United States to protect public health by ensuring the safety of drinking water. These regulations identify a number of contaminants that may pose health risks if found in significant concentrations in drinking water. It’s important to note that the presence of these contaminants doesn’t necessarily imply immediate danger, but their levels should be kept below the established maximum contaminant levels (MCLs) to ensure safety.
We have identified the necessary treatment methods for each contaminant and provided a source for you to cross reference. When dealing with these contaminants you should always consult an expert before making any decisions.
If you find this table to contain too much information, you can view a list of the most common contaminates.
| Type | Contaminant | Max. Contaminant Level Goal (ppm) | Max. Contaminant Level (ppm) -or- Required Treatment Technique | Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term) | Sources of Contaminant in Drinking Water | Consumer Treatment Method | Official Sources |
| Microorganisms | Cryptosporidium | 0 | Treatment Technique | Gastrointestinal illness (such as diarrhea, vomiting, and cramps) | Human and animal fecal waste | Boiling water, UV light treatment, microfiltration, ultrafiltration, nanofiltration, reverse osmosis system, distillation, Ozone treatment | CDC, CDC, EPA |
| Microorganisms | Giardia lamblia | 0 | Treatment Technique (99.9% removal/inactivation) | Gastrointestinal illness (such as diarrhea, vomiting, and cramps) | Human and animal fecal waste | Boiling water, UV light treatment, microfiltration, ultrafiltration, nanofiltration, reverse osmosis system, distillation, chlorination, Ozone treatment | CDC, CDC, EPA |
| Microorganisms | Heterotrophic plate count (HPC) | n/a | <= 500 bacterial colonies per mL | 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 | Regular cleaning and disinfection of water storage and distribution systems | CDC |
| Microorganisms | Legionella | 0 | Treatment Technique (no limit, but considered controlled if Giardia and viruses removed/inactivated) | Legionnaire’s Disease, a type of pneumonia | Found naturally in water; multiplies in heating systems | Heat (temperatures above 60°C/140°F), chlorination, UV light treatment, ozone. | CDC, EPA |
| Microorganisms | Total Coliforms (including fecal coliform and E. Coli) Quick reference guide Rule Summary | 0 | No more than 5% of samples test positive for coliform in a month | Used to indicate whether potentially harmful bacteria are present | Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste. | Chlorination, UV light treatment, ultrafiltration, nanofiltration, reverse osmosis systems, distillation, ozone treatment | CDC, CDC |
| Microorganisms | Turbidity | n/a | Treatment Technique (<0.3 Nephelometric Turbidity Unit) | 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 | Filtration systems | EPA |
| Microorganisms | Viruses (enteric) | 0 | Treatment Technique (99.9% removal/inactivation) | Gastrointestinal illness (such as diarrhea, vomiting, and cramps) | Human and animal fecal waste | Boiling water, UV light treatment, nanofiltration, reverse osmosis, distillation | CDC, CDC, EPA |
| Disinfection Byproducts | Bromate | 0 | 0.01 | Increased risk of cancer | Byproduct of drinking water disinfection | Activated Carbon Filtration, Aeration | EPA, EPA |
| Disinfection Byproducts | Chlorite | 0.8 | 1 | Anemia; nervous system effects in infants and young children | Byproduct of drinking water disinfection | Activated Carbon Filtration, Aeration | EPA, EPA |
| Disinfection Byproducts | Haloacetic acids (HAA5) | Varies depending on specific HAA5 | 0.06 | Increased risk of cancer | Byproduct of drinking water disinfection | Activated Carbon Filtration, Aeration | EPA, EPA |
| Disinfection Byproducts | Total Trihalomethanes (TTHMs) | Varies depending on specific TTHM | 0.08 | Liver, kidney or central nervous system problems; increased risk of cancer | Byproduct of drinking water disinfection | Activated Carbon Filtration, Aeration | EPA, EPA |
| Disinfectants | Chloramines (as Cl2) | 4 | 4 | Eye/nose irritation; stomach discomfort, anemia | Water additive used to control microbes | Activated Carbon Filtration, Reverse Osmosis, Boiling, Distillation | EPA |
| Disinfectants | Chlorine (as Cl2) | 4 | 4 | Eye/nose irritation; stomach discomfort | Water additive used to control microbes | Activated Carbon Filtration, Reverse Osmosis, Boiling, Distillation | EPA |
| Disinfectants | Chlorine dioxide (as ClO2) | 0.8 | 0.8 | Anemia; nervous system effects in infants and young children | Water additive used to control microbes | Activated Carbon Filtration, Reverse Osmosis, Boiling, Distillation | EPA |
| Inorganic Chemicals | Antimony | 0.006 | 0.006 | Increase in blood cholesterol; decrease in blood sugar, lung and heart damage | Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder | Reverse Osmosis, Activated Alumina | EPA, CDC |
| Inorganic Chemicals | Arsenic | 0 | 0.01 | Skin damage or problems with circulatory systems, and may have increased risk of getting cancer | Erosion of natural deposits; runoff from orchards and cotton farms, runoff from glass and electronics production wastes | Reverse Osmosis, Activated Alumina, Distillation, Ion Exchange, GFO/GFH | CDC, NSF, EPA, CDC |
| Inorganic Chemicals | Asbestos (fiber > 10 micrometers) | 7 million fibers per liter (MFL) | 7 MFL | Increased risk of developing benign intestinal polyps, possible link to stomach cancer | Decay of asbestos cement in water mains; erosion of natural deposits | Reverse Osmosis, Activated Carbon | NSF, WHO |
| Inorganic Chemicals | Barium | 2 | 2 | Increase in blood pressure | Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits | Reverse Osmosis, Distillation, Ion Exchange | CDC, NSF, EPA |
| Inorganic Chemicals | Beryllium | 0.004 | 0.004 | Intestinal lesions | Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries | Reverse Osmosis, Activated Alumina | EPA |
| Inorganic Chemicals | 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 | Reverse Osmosis, Distillation, Activated Carbon | CDC, NSF |
| Inorganic Chemicals | Chromium (total) | 0.1 | 0.1 | Allergic dermatitis | Discharge from steel and pulp mills; erosion of natural deposits | Reverse Osmosis, Distillation | CDC, NSF |
| Inorganic Chemicals | Copper | 1.3 | Treatment Technique on Corrosiveness of Water Action Level=1.3ppm | 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 | pH Adjustment, Ion Exchange, Reverse Osmosis | CDC, NSF, EPA |
| Inorganic Chemicals | Cyanide (as free cyanide) | 0.2 | 0.2 | Nerve damage, heart or thyroid problems | Discharge from steel/metal factories; discharge from plastic and fertilizer factories | Reverse Osmosis, Activated Carbon, Ion Exchange | CDC, EPA |
| Inorganic Chemicals | Fluoride | 4 | 4 | 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 | Activated Alumina, Reverse Osmosis, Distillation | CDC, NSF, EPA |
| Inorganic Chemicals | Lead | 0 | Treatment Technique on Corrosiveness of Water 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 | Reverse Osmosis, Distillation, Activated Carbon, pH adjustment | CDC, NSF, EPA |
| Inorganic Chemicals | Mercury (inorganic) | 0.002 | 0.002 | Kidney damage | Erosion of natural deposits; discharge from refineries and factories; runoff from landfills and croplands | Activated Carbon, Reverse Osmosis Distillation | EPA, Nature |
| Inorganic Chemicals | 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; leaking from septic tanks, sewage; erosion of natural deposits | Reverse Osmosis, Distillation, Ion Exchange, Biological treatment | CDC, NSF, EPA |
| Inorganic Chemicals | 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; leaking from septic tanks, sewage; erosion of natural deposits | Reverse Osmosis, Distillation | NSF |
| Inorganic Chemicals | 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 | Reverse Osmosis, Activated Carbon, Ion Exchange, Activated Alumina | CDC, NSF, EPA |
| Inorganic Chemicals | 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 | Activated Carbon, Reverse Osmosis, Activated Alumina | EPA |
| Organic Chemicals | Acrylamide | 0 | Treatment Technique, cannot use concentration higher than 0.05% at a dose of 1mg/L | Nervous system or blood problems; increased risk of cancer | Added to water during sewage/wastewater treatment | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Alachlor | 0 | 0.002 | Eye, liver, kidney or spleen problems; anemia; increased risk of cancer | Runoff from herbicide used on row crops | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Atrazine | 0.003 | 0.003 | Cardiovascular system or reproductive problems | Runoff from herbicide used on row crops | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Benzene | 0 | 0.005 | Anemia; decrease in blood platelets; increased risk of cancer | Discharge from factories; leaching from gas storage tanks and landfills | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Benzo(a)pyrene (PAHs) | 0 | 0.0002 | Reproductive difficulties; increased risk of cancer | Leaching from linings of water storage tanks and distribution lines | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Carbofuran | 0.04 | 0.04 | Problems with blood, nervous system, or reproductive system | Leaching of soil fumigant used on rice and alfalfa | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Carbon tetrachloride | 0 | 0.005 | Liver problems; increased risk of cancer | Discharge from chemical plants and other industrial activities | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Chlordane | 0 | 0.002 | Liver or nervous system problems; increased risk of cancer | Residue of banned termiticide | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Chlorobenzene | 0.1 | 0.1 | Liver or kidney problems | Discharge from chemical and agricultural chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | 2,4-D | 0.07 | 0.07 | Kidney, liver, or adrenal gland problems | Runoff from herbicide used on row crops | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Dalapon | 0.2 | 0.2 | Minor kidney changes | Runoff from herbicide used on rights of way | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | 1,2-Dibromo-3-chloropropane (DBCP) | 0 | 0.0002 | Reproductive difficulties; increased risk of cancer | Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | o-Dichlorobenzene | 0.6 | 0.6 | Liver, kidney, or circulatory system problems | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | p-Dichlorobenzene | 0.075 | 0.075 | Anemia; liver, kidney or spleen damage; changes in blood | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | 1,2-Dichloroethane | 0 | 0.005 | Increased risk of cancer | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | 1,1-Dichloroethylene | 0.007 | 0.007 | Liver problems | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | cis-1,2-Dichloroethylene | 0.07 | 0.07 | Liver problems | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | trans-1,2-Dichloroethylene | 0.1 | 0.1 | Liver problems | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Dichloromethane | 0 | 0.005 | Liver problems; increased risk of cancer | Discharge from drug and chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | 1,2-Dichloropropane | 0 | 0.005 | Increased risk of cancer | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Di(2-ethylhexyl) adipate | 0.4 | 0.4 | Weight loss, liver problems, or possible reproductive difficulties. | Discharge from chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Di(2-ethylhexyl) phthalate | 0 | 0.006 | Reproductive difficulties; liver problems; increased risk of cancer | Discharge from rubber and chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Dinoseb | 0.007 | 0.007 | Reproductive difficulties | Runoff from herbicide used on soybeans and vegetables | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Dioxin (2,3,7,8-TCDD) | 0 | 0.00000003 | Reproductive difficulties; increased risk of cancer | Emissions from waste incineration and other combustion; discharge from chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Diquat | 0.02 | 0.02 | Cataracts | Runoff from herbicide use | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Endothall | 0.1 | 0.1 | Stomach and intestinal problems | Runoff from herbicide use | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Endrin | 0.002 | 0.002 | Liver problems | Residue of banned insecticide | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Epichlorohydrin | 0 | Treatment Technique, cannot use concentration higher than 0.01% at a dose of 20mg/L | Increased cancer risk, stomach problems | Discharge from industrial chemical factories; an impurity of some water treatment chemicals | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Ethylbenzene | 0.7 | 0.7 | Liver or kidneys problems | Discharge from petroleum refineries | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Ethylene dibromide | 0 | 0.00005 | Problems with liver, stomach, reproductive system, or kidneys; increased risk of cancer | Discharge from petroleum refineries | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Glyphosate | 0.7 | 0.7 | Kidney problems; reproductive difficulties | Runoff from herbicide use | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Heptachlor | 0 | 0.0004 | Liver damage; increased risk of cancer | Residue of banned termiticide | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Heptachlor epoxide | 0 | 0.0002 | Liver damage; increased risk of cancer | Breakdown of heptachlor | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Hexachlorobenzene | 0 | 0.001 | Liver or kidney problems; reproductive difficulties; increased risk of cancer | Discharge from metal refineries and agricultural chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Hexachlorocyclopentadiene | 0.05 | 0.05 | Kidney or stomach problems | Discharge from chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Lindane | 0.0002 | 0.0002 | Liver or kidney problems | Runoff/leaching from insecticide used on cattle, lumber, gardens | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Methoxychlor | 0.04 | 0.04 | Reproductive difficulties | Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Oxamyl (Vydate) | 0.2 | 0.2 | Slight nervous system effects | Runoff/leaching from insecticide used on apples, potatoes, and tomatoes | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Polychlorinated biphenyls (PCBs) | 0 | 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 | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Pentachlorophenol | 0 | 0.001 | Liver or kidney problems; increased cancer risk | Discharge from wood preserving factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Picloram | 0.5 | 0.5 | Liver problems | Herbicide runoff | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Simazine | 0.004 | 0.004 | Problems with blood | Herbicide runoff | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Styrene | 0.1 | 0.1 | Liver, kidney, or circulatory system problems | Discharge from rubber and plastic factories; leaching from landfills | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Tetrachloroethylene | 0 | 0.005 | Liver problems; increased risk of cancer | Discharge from factories and dry cleaners | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Toluene | 1 | 1 | Nervous system, kidney, or liver problems | Discharge from petroleum factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Toxaphene | 0 | 0.003 | Kidney, liver, or thyroid problems; increased risk of cancer | Runoff/leaching from insecticide used on cotton and cattle | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | 2,4,5-TP (Silvex) | 0.05 | 0.05 | Liver problems | Residue of banned herbicide | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | 1,2,4-Trichlorobenzene | 0.07 | 0.07 | Changes in adrenal glands | Discharge from textile finishing factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | 1,1,1-Trichloroethane | 0.2 | 0.2 | Liver, nervous system, or circulatory problems | Discharge from metal degreasing sites and other factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | 1,1,2-Trichloroethane | 0.003 | 0.005 | Liver, kidney, or immune system problems | Discharge from industrial chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Trichloroethylene | 0 | 0.005 | Liver problems; increased risk of cancer | Discharge from metal degreasing sites and other factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Organic Chemicals | Vinyl chloride | 0 | 0.002 | Increased risk of cancer | Leaching from PVC pipes; discharge from plastic factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, EPA |
| Organic Chemicals | Xylenes (total) | 10 | 10 | Nervous system damage | Discharge from petroleum and chemical factories | Activated carbon filtration, Reverse Osmosis, Aeration | EPA, NSF, EPA |
| Radionuclides | Alpha particles | 0 | 15 picocuries per Liter (pCi/L) | Increased risk of cancer | Erosion of natural deposits of certain minerals that are radioactive | Reverse Osmosis, Alum Treatment | EPA, EPA |
| Radionuclides | Beta particles and photon emitters | 0 | 4 millirems per year | Increased risk of cancer | Decay of natural and man-made deposits of certain minerals that are radioactive | Reverse Osmosis, Alum Treatment | EPA, EPA |
| Radionuclides | Radium 226 and Radium 228 (combined) | 0 | 5 pCi/L | Increased risk of cancer | Erosion of natural deposits | Ion Exchange, Reverse Osmosis, Alum Treatment | EPA, CDC, NSF |
| Radionuclides | Uranium | 0 | 30 ug/L | Increased risk of cancer, kidney toxicity | Erosion of natural deposits | Ion Exchange, Reverse Osmosis, Alum Treatment | EPA, EPA |
