Water and health.

The systems protecting the quality of drinking water in the United States are deteriorating. Many urban water and sewer systems are obsolete. Industrial wastes are imposing a burden on wastewater treatment facilities. In the U.S., outbreaks of water-borne disease are primarily limited to enteritis associated with viruses or Giardia. Issues in the contamination of drinking water by toxic substances include disposal practices, accidental contamination, agricultural runoff and chlorination byproducts. Physicians must support stringent enforcement of water quality standards.