Primary Drinking Water Standards
There are two categories of the EPA’s drinking water regulations. The National Primary Drinking Water Regulations include legally enforceable maximum contaminant levels (MCL) for hazardous contaminants in 6 broad categories: microorganisms, disinfection byproducts, disinfectants, inorganic chemicals, organic chemicals, and radionuclides.
Primary Contaminants
Microorganisms
| Contaminant | Primary MCL | Effects |
|---|---|---|
| Cryptosporidium | 0 | Gastrointestinal illness (such as diarrhea, vomiting, and cramps) |
| Giardia lamblia | 0 | Gastrointestinal illness (such as diarrhea, vomiting, and cramps) |
| Heterotrophic plate count (HPC) | 0 | 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. |
| Legionella | 0 | Legionnaire’s Disease, a type of pneumonia |
| Total Coliforms (including fecal coliform and E. Coli) | 5.0% | Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present |
| Turbidity | n/a | Turbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (such as whether disease-causing organisms are present). |
| Viruses (enteric) | 0 | Gastrointestinal illness (such as diarrhea, vomiting, and cramps) |
Disinfection Byproducts
| Contaminant | Primary MCL | Effects |
|---|---|---|
| Bromate | 0.010 mg/L | Increased risk of cancer |
| Chlorite | 1.0 mg/L | Anemia; infants and young children: nervous system effects |
| Haloacetic acids (HAA5) | 0.060 mg/L | Increased risk of cancer |
| Total Trihalomethanes (TTHMs) | 0.080 mg/L | Liver, kidney or central nervous system problems; increased risk of cancer |
Disinfectants
| Contaminant | Maximum Residual Disinfectant Level | Effects |
|---|---|---|
| Chloramines (as Cl2) | 4.0 mg/L | Eye/nose irritation; stomach discomfort, anemia |
| Chlorine (as Cl2) | 4.0 mg/L | Eye/nose irritation; stomach discomfort |
| Chlorine dioxide (as ClO2) | 0.08 mg/L | Anemia; infants and young children: nervous system effects |
| Total Trihalomethanes (TTHMs) | 0.080 mg/L | Liver, kidney or central nervous system problems; increased risk of cancer |
Inorganic Chemicals
| Contaminant | Maximum Contaminant Level | Effects |
|---|---|---|
| Antimony | 0.006 mg/L | Increase in blood cholesterol; decrease in blood sugar |
| Arsenic | 0.010 mg/L | Skin damage or problems with circulatory systems, and may have increased risk of getting cancer |
| Asbestos | 7 million fibers per liter | Increased risk of developing benign intestinal polyps |
| Barium | 2 mg/L | Increase in blood pressure |
| Beryllium | 0.004 mg/L | Intestinal lesions |
| Cadmium | 0.005 mg/L | Kidney damage |
| Chromium | 0.1 mg/L | Allergic dermatitis |
| Copper | 1.3 mg/L | Short term exposure: Gastrointestinal distress Long term exposure: Liver or kidney damage |
| Cyanide | 0.2 mg/L | Nerve damage or thyroid problems |
| Fluoride | 4.0 mg/L | Bone disease (pain and tenderness of the bones); Children may get mottled teeth |
| Lead | 0.015 mg/L | 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 |
| Mercury | 0.002 mg/L | Kidney damage |
| Nitrate | 10 mg/L | 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. |
| Nitrite | 1 mg/L | 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. |
| Selenium | 0.05 mg/L | Hair or fingernail loss; numbness in fingers or toes; circulatory problems |
| Thalium | 0.002 mg/L | Hair loss; changes in blood; kidney, intestine, or liver problems |
Organic Chemicals
| Contaminant | Maximum Contaminant Level | Effects |
|---|---|---|
| Acrylamide | 0 | Nervous system or blood problems; increased risk of cancer |
| Alachor | 0.002 mg/L | Eye, liver, kidney or spleen problems; anemia; increased risk of cancer |
| Atrazine | 0.003 mg/L | Cardiovascular system or reproductive problems |
| Benzene | 0.005 mg/L | Anemia; decrease in blood platelets; increased risk of cancer |
| Benzo(a)pyrene (PAHs) | 0.0002 mg/L | Reproductive difficulties; increased risk of cancer |
| Carbofuran | 0.04 mg/L | Problems with blood, nervous system, or reproductive system |
| Carbon tetrachloride | 0.005 mg/L | Liver problems; increased risk of cancer |
| Chlordane | 0.002 mg/L | Liver or nervous system problems; increased risk of cancer |
| Chlorobenzene | 0.1 mg/L | Liver or kidney problems |
| 2,4-D | 0.07 mg/L | Kidney, liver, or adrenal gland problems |
| Dalapon | 0.2 mg/L | Minor kidney changes |
| 1,2-Dibromo-3-chloropropane (DBCP) | 0.0002 mg/L | Reproductive difficulties; increased risk of cancer |
| o-Dichlorobenzene | 0.075 mg/L | Anemia; liver, kidney or spleen damage; changes in blood |
| 1,2-Dichloroethane | 0.005 mg/L | Increased risk of cancer |
| 1,1-Dichloroethylene | 0.007 mg/L | Liver problems |
| cis-1,2-Dichloroethylene | 0.07 mg/L | Liver problems |
| trans-1,2-Dichloroethylene | 0.1 mg/L | Liver problems |
| Dichloromethane | 0.005 mg/L | Liver problems; increased risk of cancer |
| 1,2-Dichloropropane | 0.005 mg/L | Increased risk of cancer |
| Di(2-ethylhexyl) adipate | 0.4 mg/L | Weight loss, liver problems, or possible reproductive difficulties. |
| Di(2-ethylhexyl) phthalate | 0.006 mg/L | Reproductive difficulties; liver problems; increased risk of cancer |
| Dinoseb | 0.007 mg/L | Reproductive difficulties |
| Dioxin (2,3,7,8-TCDD) | 0.00000003 mg/L | Reproductive difficulties; increased risk of cancer |
| Diquat | 0.02 mg/L | Cataracts |
| Endothall | 0.1 mg/L | Stomach and intestinal problems |
| Endrin | 0.02 mg/L | Liver problems |
| Epichlorohydrin | 0 | Increased cancer risk, and over a long period of time, stomach problems |
| Ethylbenzene | 0.7 mg/L | Liver or kidneys problems |
| Ethylene dibromide | 0.00005 mg/L | Problems with liver, stomach, reproductive system, or kidneys; increased risk of cancer |
| Glyphosate | 0.7 mg/L | Kidney problems; reproductive difficulties |
| Heptachlor | 0.0004 mg/L | Liver damage; increased risk of cancer |
| Heptachlor epoxide | 0.0002 mg/L | Liver damage; increased risk of cancer |
| Hexachlorobenzene | 0.001 mg/L | Liver or kidney problems; reproductive difficulties; increased risk of cancer |
| Hexachlorocyclopentadiene | 0.05 mg/L | Kidney or stomach problems |
| Hexachlorocyclopentadiene | 0.05 mg/L | Kidney or stomach problems |
| Lindane | 0.0002 mg/L | Liver or kidney problems |
| Methoxychlor | 0.04 mg/L | Reproductive difficulties |
| Oxamyl (Vydate) | 0.2 mg/L | Slight nervous system effects |
| Polychlorinated biphenyls (PCBs) | 0.0005 mg/L | Skin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer |
| Pentachlorophenol | 0.001 mg/L | Liver or kidney problems; increased cancer risk |
| Picloram | 0.5 mg/L | Liver problems |
| Simazine | 0.004 mg/L | Problems with blood |
| Styrene | 0.1 mg/L | Liver, kidney, or circulatory system problems |
| Tetrachloroethylene | 0.005 mg/L | Liver problems; increased risk of cancer |
| Toluene | 1 mg/L | Nervous system, kidney, or liver problems |
| Toxaphene | 0.003 mg/L | Kidney, liver, or thyroid problems; increased risk of cancer |
| 2,4,5-TP (Silvex) | 0.05 mg/L | Liver problems |
| 1,2,4-Trichlorobenzene | 0.07 mg/L | Changes in adrenal glands |
| 1,1,1-Trichloroethane | 0.2 mg/L | Liver, nervous system, or circulatory problems |
| 1,1,2-Trichloroethane | 0.005 mg/L | Liver, kidney, or immune system problems |
| Trichloroethylene | 0.005 mg/L | Liver problems; increased risk of cancer |
| Vinyl chloride | 0.002 mg/L | Increased risk of cancer |
| Xylenes (total) | 10 mg/L | Nervous system damage |
Radionuclides
| Contaminant | Primary MCL | Effects |
|---|---|---|
| Alpha particles | 15 picocuries per Liter (pCi/L) | Increased risk of cancer |
| Beta particles and photon emitters | 4 millirems per year | Increased risk of cancer |
| Radium 226 and Radium 228 (combined) | 5 pCi/L | Increased risk of cancer |
| Uranium | 30 ug/L | Increased risk of cancer, kidney toxicity |
Secondary Drinking Water Standards
Non-mandatory regulations provide secondary maximum contamination levels (SMCL) to suggest acceptable levels of 15 additional contaminants. The National Secondary Drinking Water Regulations help manage aesthetic qualities such as taste, color, and odor, rather than human health qualities.
Secondary Contaminants
| Contaminant | Secondary MCL | Effects |
|---|---|---|
| Aluminum | 0.05 to 0.2 mg/L | colored water |
| Chloride | 250 mg/L | salty taste |
| Color | 15 color units | visible tint |
| Copper | 1.0 mg/L | metallic taste; blue-green staining |
| Corrosivity | Non-corrosive | metallic taste; corroded pipes/fixtures staining |
| Fluoride | 2.0 mg/L | tooth discoloration |
| Foaming Agents | 0.5 mg/L | frothy, cloudy; bitter taste; odor |
| Iron | 0.3 mg/L | rusty color; sediment; metallic taste; reddish or orange staining |
| Manganese | 0.05 mg/L | black to brown color; black staining; bitter metallic taste |
| Odor | 3 TON (threshold odor number)/L | “rotten-egg”, musty or chemical smell |
| pH | 6.5 – 8.5 | low pH: bitter metallic taste; corrosion high pH: slippery feel; soda taste; deposits |
| Silver | 0.1 mg/L | skin discoloration; graying of the white part of the eye |
| Sulfate | 250 mg/L | salty taste |
| Total Dissolved Solids (TDS) | 500 mg/L | hardness; deposits; colored water; staining; salty taste |
| Zinc | 5 mg/L | metallic taste |
Citations
Environmental Protection Agency, National Primary Drinking Water Regulations, https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations (accessed September 19, 2017).
Images: “Pouring water from bottle” by Africa Studio via Shutterstock
