Chemical contaminants occur in drinking water supplies throughout the United States, ranging from barely detectable amounts to levels that threaten human health. Determining the health effects of these contaminants is difficult, especially since researchers are still learning how chemicals react in the body, damage human 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.
Most levels of chemicals in drinking water, however, are seldom high enough to cause acute health problems. They are more likely to cause chronic health problems, which 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. Scientists often predict 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, and are rarely based on documented studies with human subjects.
In setting drinking water standards, regulators estimate the amount of a contaminant a person can drink safely over a lifetime. These calculations are based on all available toxicological information and allow a generous safety margin. The following chart 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 as possible 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. 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.
Contaminants are regulated when they occur in drinking water supplies, are expected to threaten public health and can be detected by laboratory methods. The EPA and the State of Maine continue to set standards for many other drinking water contaminants not listed in this fact sheet that meet these criteria.
Inorganics
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Contaminant Source Possible chronic health effects1
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Arsenic rocks and soil; commercial skin and lung cancer; liver
phosphates in fertilizers and kidney damage
and laundry detergents; MCL: 0.05 mg/L2
pesticide residues; MCLG: 0.05 mg/L
smelting, glass making,
and coal mining
Asbestos corrosion of asbestos- lung cancer; gastrointestinal
cement pipe in water cancer when swallowed fibers
distribution systems; exceed 10 um
manufacture of cement MCL: NA
products, paper, floor MCLG: 7.1 million fibers >
tiles, paint, caulking, (10 um long)/liter
textiles and plastics
Barium rocks and soil; coal and hypertension and heart damage
gas mining; coal burning; MCL: 1.0 mg/L
diesel fuel combustion and MCLG: 1.5 mg/L
jet fuel; paints, bricks
and tiles
Cadmium rocks, coal, and petroleum; kidney damage
by-products of mining, MCL: 0.010 mg/L
smelting, refining and MCLG: 0.005 mg/L
electroplating;.discarded
batteries, paints, and
plastics; corrosion of
galvanized pipe; landfills
and industrial waste sites;
fertilizers and sewage
sludge
Chromium rocks and soil; mining liver, kidney and lung damage
sites, chrome plating, MCL: 0.05 mg/L
cement production; waste MCLG: 0.12 mg/L
incineration; contaminated
laundry detergent and
bleaches;septic systems
Copper rocks and soil; coal anemia; digestive disturbances;
burning, iron and steel liver and kidney damage
production; industrial and MCL: 1.3 mg/L
sewage treatment plant MCLG: 1.3 mg/L
wastes; corrosion of brass
and copper pipes
Fluoride rocks and soil; industrial mottling of teeth; bone damage
wastes MCL: 4.0 mg/L
MCLG: 4.0 mg/L
Lead rocks and soil; corrosion brain and nerve damage;
of lead pipes and lead- especially in children; kidney
soldered pipe joints; damage; digestive disturbances;
combustion of leaded blood disorders; hypertension
gasoline; smelter emissions MCL: 0.005 mg/L
and discarded storage MCLG: 0 mg/L
batteries
Mercury soil and rocks; mining, brain and nerve damage; kidney
smelting, coal burning; damage; birth defects and skin
electrical equipment and rash
fungicides MCL: 0.002 mg/L
MCLG: 0.003 mg/L
Nitrate soils and mineral deposits; Methemoglobinamia in infants
fertilizers, sewage and MCL: 10 mg/L nitrate-nitrogen
animal wastes 45 mg/L nitrate
MCLG: 10 mg/L nitrate-nitrogen
45 mg/L nitrate
Selenium soil and shales; coal growth inhibition; skin
burning mining, smelting; discoloration; dental and
manufacture of glass, digestive problems; liver damage
paints, and drugs; and psychological disorders
fungicides and feed MCL: 0.01 mg/L
additives MCLG: 0.045 mg/L
Silver soil, coal, and mineral agyria, a permanent blue-gray
deposits; ore mining and discoloration of skin, mucous
manufacture of alloys; membranes and eyes
photographic procedures MCL: 0.05 mg/L
and jewelry making MCLG: NA
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1 The units of measurement are milligrams per liter (mg/L), micrometers (um)
and picoCuries (pCi).
2 Maine standards are constantly being updated. Check with the Maine Department
of Human Services for revised quantities.
Organics
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Contaminant Source Possible chronic health effects1
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Acrylamide drinking water treatment cancer and nervous system
residue; well drilling; effects
food production and MCL: NA
processing; papermaking MCLG: 0 mg/L
and textile manufacturing
Alachlor agricultural herbicide cancer; damage to eyes and liver
MCL: NA
MCLG: 0 mg/L
Aldicarb agricultural insecticide cholinesterase inhibition
MCL: NA
MCLG: 0.009 mg/L
Benzene leaking underground fuel leukemia and other cancers;
storage tanks; industrial nerve, lung and kidney damage;
wastes; manufacture of blood disorders and reproductive
pesticides, detergents and effects
solvents MCL: 0.005 mg/L
MCLG: 0 mg/L
Carbofuran agricultural insecticide Cholinesterase inhibition;
reproductive and immune
system effects
MCL: NA
MCLG: 0.036 mg/L
Chlordane insecticide; hazardous cancer; nerve and liver effects
waste sites MCL: NA
MCLG: 0 mg/L
2,4-D agricultural herbicide liver and kidney damage; skin
and aquatic weeds control irritations and muscle effects
MCL: 0.01 mg/L
MCLG: 0.07 mg/L
Dibromo- soil fumigant cancer; kidney and liver damage,
chloropropane infertility
(DBCP) MCL: NA
MCLG: 0 mg/L
p-Dichlorobezene dye and pesticide liver and kidney damage; blood
manufacturing disorder
MCL: 0.075 mg/L
MCLG: 0.075 mg/L
1,2-Dichlorobezene vinyl manufacturing, dry cancer; central nervous system
cleaning solvent, metal depression; kidney and liver
degreasers, and adhesives; damage; lung and heart damage
gasoline additive MCL: 0.005 mg/L
MCLG: 0 mg/L
1,1-Dichlorobezene industrial solvent, central nervous system
cleaning and degreasing depression; liver, kidney and
agent heart damage
MCL: 0.007 mg/L
MCLG: 0.007 mg/L
cis and trans transformed from other liver and kidney damage
1,2-Dichloroehtylene chlorinated hydrocarbons MCL: NA
in drinking water MCLG: 0.07 mg/L
supplies; industrial
cleaning and degreasing
agents
1,2-Dichloropropane industrial solvent and liver and kidney damage
cleaning agents; dry MCL: NA
cleaning fluid components, MCLG: 0.006 mg/L
soil fumigants
Endrin insecticide and liver and nervous system
rodenticide effects; birth defects
MCL: 0.0002 mg/L
MCLG: NA
Epichlorohydrin resin and rubber product cancer; central nervous system,
manufacturing; lung, liver and kidney effects;
contamination of materials damage to male reproductive
used to process food and organ
treat or store drinking MCL: NA
water MCLG: 0 mg/L
Ethyl benzene hazardous waste sites and nerve, brain, liver and kidney
styrene production effects
MCL: NA
MCLG: 0.68 mg/L
Ethylene pesticide and soil cancer; liver, kidney, nervous
dibromide fumigants; leaded gasoline system, gastrointestinal and
additives reproductive effects
MCL: NA
MCLG: 0 mg/L
Heptachlor/ insecticide and hazardous cancer; liver damage and central
Heptachlor Epoxide waste sites nervous system effects
MCL: NA
MCLG: 0 mg/L
Lindane pesticides liver and kidney damage
MCL: 0.004 mg/L
MCLG: 0.0002 mg/L
Methoxychlor insecticides nervous system, kidney, and
liver effects
MCL: .10 mg/L
MCLG: 0.34 mg/L
Pentachlorophenol herbicides and liver and kidney damage;
(PCP) insecticides; water nervous system,immune system,
contact with PCP- treated and reproductive effects; blood
wood; industrial waste disorders
sites MCL: NA
MCLG: 0.22 mg/L
Polychlorinated hazardous waste sites; cancer; liver damage
Biphenyls (PCBS) disposals and manufacture MCL: NA
of electrical transformers, MCLG: 0 mg/L
electromagnets, fluorescent
lights and plastics
Styrene manufacture of plastics, liver damage
synthetic rubbers, resins, MCL: NA
and insulators MCLG: 0.14 mg/L
Tetrachloroethylene industrial metal, textile, cancer; liver and kidney damage;
and dry cleaning solvent central nervous system
depression
MCL: NA
MCLG: NA
Toluene paint, oil, resin central nervous system
manufacturing; leaking depression; kidney damage
fuel storage tanks; jet MCL: NA
fuel MCLG: 2.0 mg/L
Toxaphene insecticides cancer, liver and kidney damage
MCL: 0.005 mg/L
MCLG: 0 mg/L
2,4,5-TP (Silvex) herbicides liver and kidney damage
MCL: 0.010 mg/L
MCLG: 0.052 mg/L
1,1,1- hazardous waste sites; central nervous system
Trichloroethene industrial solvent and depression; liver and
degreasers; drycleaning cardiovascular damage
solvents MCL: 0.20 mg/L
MCLG: 0.20 mg/L
Trichloroethylene hazardous waste sites; cancer; nervous system
(TCE) drycleaning solvent; depression and heart effects;
manufacturing of chemicals liver and kidney damage
and drugs MCL: 0.005 mg/L
MCLG: 0 mg/L
Total formed when residual cancer; heart, lung, kidney and
Trihalomethanes chlorine in treated liver damage
drinking water combines MCL: 0.100 mg/L
with naturally occurring MCLG: NA
organic matter
Vinyl Chloride manufacturing of plastics cancer; central nervous system
and synthetic rubber; depression; liver reproductive,
corrosion of plastic pipes and digestive tract effects,
and soldering birth defects
MCL: 0.002 mg/L
MCLG: 0 mg/L
Xylene leaking underground fuel nervous system and reproductive
storage tanks; effects
of chemicals and drugs MCL: NA
MCLG: 0.44 mg/L
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Microbial Pathogens
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Contaminant Source Possible chronic health effects
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Coliform Bacteria sewage, animal wastes; gastroenteritis, salmonella
(an indicator backflow or improper pipe infection, dysentery,
organism for connections in water typhoid fever and cholera
fecal coliform, systems; improperly sealed MCL: < 1/100ml
streptococcal, or constructed wells MCLG: 0 mg/L
and other
pathogenic
bacteria).
Giardia lamblia sewage and animal wastes giardiasis (a gastrointestinal
infection causing diarrhea,
abdominal cramps and gas)
MCL: NA
MCLG: 0 mg/L
Viruses sewage gastroenteritis and other viral
diseases; hepatitis
MCL: NA
MCLG: 0 mg/L
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Radioactive Elements
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Contaminant Source Possible chronic health effects
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Gross Alpha natural decay of uranium cancer; bone and kidney damage
Particles in rocks and soil MCL: 15 pCi/L
MCLG: NA
Radium-226, -228 natural decay of uranium bone cancer; bone and kidney
in rocks and soil damage; birth defects
MCL: 5 pCi/L
MCLG: pending
Radon decay of uranium in soils lung cancer, when released as
and rocks a gas and inhaled
MCL: NA
MCLG: NA
Uranium soil and rocks cancer and kidney damage
MCL: NA
MCLG: NA
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_________1985. National Primary Drinking Water Regulations; Volatile Synthetic Organic Chemicals. Federal Register 50(219): 46879-46934.
_________1985. National Primary Drinking Water Regulations; Synthetic Organic Chemicals, Inorganic Chemicals and Microorganisms. Federal Register 50(219): 46935-47022.
_________1987. National Primary Drinking Water Regulations; Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants. Federal Register 52(130): 25690-25734.
Boyd, S., A. Jones, A. Knaus and C. McGrath (eds.). 1986. Drinking Water: A Community Action Guide. Concern, Inc., Washington, D.C.
Council on Environmental Quality. 1981. Contamination of Ground Water by Toxic Organic Chemicals. U.S. Government Printing Office, Washington, D.C.
Safe Drinking Water Committee. National Academy of Sciences, National Research Council. 1986. Drinking Water and Health, volume 6. National Academy Press, Washington, D.C.
WaterTest Corporation. 1986. Manual, 6th edition. Manchester, NH.
"Regulated Contaminants and Their Health Effects." EPA Journal 12(7): 26-28.
For more information on water quality concerns, contact your county Extension office.
Originally written and produced by Cornell University and the University of Maryland under the sponsorship of USDA Extension Service. Adapted from Cooperative Extension System Water Quality Fact Sheet #2. This material is based on work supported by the U. S. Department of Agriculture, Extension Service, under special project number 90-EWQI-1-9231.
