- Topics: Soil and Water Science | Drinking Water | Hornsby, Arthur G

Chemical contaminants occur in drinking water supplies throughout the United States, ranging from barely detectable amounts to levels that could possibly threaten human health. Determining the health effects of these contaminants is difficult, especially since researchers are still learning how chemicals react in the body to damage cells and cause illness.
Toxic doses of chemicals cause either acute or chronic health effects. An acute effect usually follows a large dose of a chemical and occurs almost immediately. Examples of acute health effects are nausea, lung irritation, skin rash, vomiting, dizziness and even death.
The levels of chemicals in drinking water, however, are seldom high enough to cause acute health effects. They are more likely to cause chronic health effects that occur long after exposure to small amounts of a chemical. Examples of chronic health effects include cancer, birth defects, organ damage, disorders of the nervous system, and damage to the immune system.
Evidence relating chronic health effects to specific drinking water contaminants is limited. In the absence of exact scientific information, scientists predict the likely adverse effects of chemicals in drinking water using laboratory animal studies and, when available, human data from clinical reports and epidemiological studies. The possible chronic health effects of the chemicals listed in this fact sheet are conservative estimates, rarely based on documented human health effects.
In setting standards for drinking water contaminants, regulators estimate the concentration of a contaminant that a person can drink safely over a lifetime. These calculations are based on all available toxicological informarion and allow a generous safety margin. Table 1 lists contaminants currently regulated by U.S. Environmental Protection Agency (EPA) standards.
The EPA standard for drinking water, the Maximum Contaminant Level (MCL), is the highest amount of a contaminant allowed in drinking water supplied by municipal water systems. The MCL is set as close to the Maximum Contaminant Level Goal (MCLG), which is a preliminary standard set but not enforced by the EPA. MCLGs are health goals based entirely on health effects, but MCLs also take into consideration the feasibility and cost of analysis and treatment of the regulated contaminant. Although often less stringent than the corresponding MCLG, the MCL is set to protect health. When there is no reliable method that is economically and technically feasible to measure a contaminant at particularly low concentrations, a Treatment Technique (TT) is set rather than an MCL. A treatment technique (TT) is an enforceable procedure or level of technological performance which public water systems must follow to ensure control of a contaminant. Treatment Techniques are listed in "Notes".
Contaminants are regulated when they occur in drinking water supplies and, are expected to threaten public health and, can be detected in drinking water by current laboratory methods. The EPA will continue to set standards for many other drinking water contaminants not listed in this fact sheet which meet these criteria.
Treatment Technique An enforceable procedure or level of technical performance which public water systems must follow to ensure control of a contaminant.
Units are in milligrams per Liter (mg/L) unless otherwise noted.
MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no MCLG for this contaminant.
Lead and copper are regulated in a Treatment Technique which requires systems to take tap water samples at sites with lead pipes or copper pipes that have lead solder and/or are served by lead service lines. The action level which triggers water systems into taking treatment steps, if exceeded in more than 10% of tap water samples, is for copper: 1.3 mg/L, and for lead: 0.015mg/L.
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)
The Surface Water Treatment Rule requires systems using surface water or ground water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water to meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels:
Giardia lamblia: 99.9% killed/inactivated
Viruses: 99.99% killed/inactivated
Legionella: No limit, but EPA believes that if Giardia and viruses are 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. HPC: NO more than 500 bacterial colonies per milliliter.
No more than 5.0% samples total coliformin a month. (For water systems that collect fewer than 40 routine samples per month, no more than one sample can be total coliform. Every sample that has total coliforms must be analyzed for fecal coliforms. There cannot be any fecal coliforms.
Contaminants currently regulated by U.S. Environmental Protection Agency (EPA) standards.
Contaminant |
MCLG 1 (mg/L)4 |
MCL2 or TT3 (mg/L)4 |
Potential Health Effects from Ingestion of Water |
Sources of Contaminant in Drinking Water |
Inorganic Chemicals |
||||
Antimony |
0.006 |
0.006 |
Increase in blood cholesterol; decrease in blood glucose |
Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder |
Arsenic |
none5 |
0.05 |
Skin damage; circulatory system problems; increased risk of cancer |
Discharge from semiconductor manufacturing; petroleum refining; wood preservatives; animal feed additives; herbicides; erosion of natural deposits |
Asbestos (fiber >10 micrometers) |
7 million fibers per Liter (MFL) |
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 coalfactories; 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 |
Some people who use water containing chromium well in excess of the MCL over many years could experience allergic dermatitis |
Discharge from steel and pulp mills; erosion of natural deposits |
Copper |
1.3 |
Action Level=1.3; TT6 |
Short term exposure: Gastrointestinal distress. |
Corrosion of household plumbing systems; erosion of natural deposits; leaching from wood preservatives |
Long term exposure: Liver or kidney damage. Those with Wilson's Disease should consult their personal doctor if their water systems exceed the copper action level. |
||||
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 |
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 |
Lead |
zero |
Action Level= |
Infants and children: Delays in physical or mental development. |
Corrosion of household plumbing systems; erosion of natural deposits |
0.015; TT6 |
Adults: Kidney problems; high blood pressure |
|||
Inorganic Mercury |
0.002 |
0.002 |
Kidney damage |
Erosion of natural deposits; discharge from refineries and factories; runoff from landfills and cropland |
Nitrate (measured as Nitrogen) |
10 |
10 |
"Blue baby syndrome" in infants under six months life threatening without immediate medical attention. |
Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits |
Symptoms: Infant looks blue and has shortness of breath. |
||||
Nitrite (measured as Nitrogen) |
1 |
1 |
"Blue baby syndrome" in infants under six months life threatening without immediate medical attention. |
Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits |
Symptoms: Infant looks blue and has shortness of breath. |
||||
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 oresites; discharge from electronics, glass, and pharmaceutical companies |
Organic Chemicals |
||||
Acrylamide |
zero |
TT7 |
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 problems; reproductive difficulties |
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 |
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 or nervous system; reproductive difficulties. |
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 |
Discharger 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 pharmaceutical 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 |
General toxic effects or reproductive difficulties |
Leaching from PVC plumbing systems; 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 |
3.0x10-8 |
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 |
Nervous system effects |
Residue of banned insecticide |
Epichlorohydrin |
zero |
TT7 |
Stomach problems; reproductive difficulties; increased risk of cancer |
Discharge from industrial chemical factories; added to water during treatment process |
Ethylbenzene |
0.7 |
0.7 |
Liver or kidney problems |
Discharge from petroleum refineries |
Ethelyne dibromide |
zero |
0.00005 |
Stomach problems; reproductive difficulties; 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 hepatachlor |
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 catttle, 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 difficiencies; reproductive or nervous system difficulties; increased risk of cancer |
Runoff from landfils; discharge of waste chemicals |
Pentachlorophenol |
zero |
0.001 |
Liver or kidney problems; increased risk of cancer |
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, and circulatory 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 |
Total Trihalomethanes (TTHMs) |
none5 |
0.1 |
Liver, kidney or central nervous system problems; increased risk of cancer |
Byproduct of drinking water disinfection |
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 |
0.2 |
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 petroleum refineries |
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 |
||||
Beta particles and photon emitters |
none5 |
4 millirems per year |
Increased risk of cancer |
Decay of natural and mandeposits |
Gross alpha particle activity |
none5 |
15 picocuries per Liter (pCi/L) |
Increased risk of cancer |
Erosion of natural deposits |
Radium 226 and Radium 228 (combined) |
none5 |
5 pCi/L |
Increased risk of cancer |
Erosion of natural deposits |
Microorganisms |
||||
Giardia lamblia |
zero |
TT8 |
Giardiasis, a gastroenteric disease |
Human and animal fecal waste |
Heterotrophic plate count |
N/A |
TT8 |
HPC has no health effects, but can indicate how effective treatment is at controlling microorganisms. |
n/a |
Legionella |
zero |
TT8 |
Legionnaire's Disease, commonly known as pneumonia9 |
Found naturally in water; multiplies in heating systems |
Total Coliforms (including fecal coliform and E. Coli) |
zero |
5.0%9 |
Used as an indicator that other potentially harmful bacteria may be present10 |
Human and animal fecal waste |
Turbidity |
N/A |
TT8 |
Turbidity has no health effects but can interfere with disinfection and provide a medium for microbial growth. It may indicate the presence of microbes. |
Soil runoff |
Viruses (enteric) |
zero |
TT8 |
Gastroenteric disease (e.g. diarrhea, vomiting, cramps) |
Human and animal fecal waste. |
This document is SL161, a series of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published February 2001 Please visit the EDIS Web site at http://edis.ifas.ufl.edu.
Judith C. Stewart, extension support aide, Ann T. Lemley, associate professor, College of Human Ecology, Cornell University, Sharon I. Hogan, communications consultant, and Richard A. Weismiller, soil and water resource specialist, Department of Agronomy, University of Maryland., Arthur G. Hornsby, professor, Soil and Water Science Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611-0290. Originally written and produced in 1988, revised 1988-89, by Cornell University and the University of Maryland under the sponsorship of the USDA Extension Service.
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