Health Effects of Drinking Water Contaminants

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Possible Chronic Health Effects

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.

Setting Standards

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 continues to set standards for many other drinking water contaminants not listed in this fact sheet that meet these criteria.

Regulated Contaminants

Note 1: The units of measurement are milligrams per liter (mg/L), micrometers (um) and picoCuries (pCi).
Note 2: Standards are constantly being updated. Check with your local Department of Human Services for revised quantities.

REFERENCES

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.

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.