The Environmental Protection Agency is in the process of setting standards for 83 contaminants in drinking water, but meantime thousands of communities in 30 states have water contamination problems.

Contaminated water can cause liver and kidney damage, cancer, sterility and mental retardation in children, according to an article in the current issue of Redbook, and one expert called it a national crisis."If you live near a military base, industrial factory, electronics plant, mine, airport, farmland or any kind of dump site, your water could be seriously contaiminated," said investigative reporter Jonathan King, author of "Troubled Water," a study of the nation's water supply.

"A 1983 Environmental Protection Agency report on large public water systems found that more than 20 percent were contaminated. Water quality has become a national crisis."

The majority of U.S. water systems are regulated by the federal Safe Drinking Water Act, which gives the EPA authority to set exposure limits for everything in water that may pose a health hazard.

Currently, the EPA has standards for bacteria; 10 inorganic chemicals including arsenic, lead and mercury; 15 organic chemicals; anything that releases radium and total radioactivity.

"Were in the process of setting standards for 83 contaminants," said Jeanne Briskin, special assistant to the director of EPA's Office of Drinking Water. "Once these new limits are finalized by 1989, we'll have standards for nearly all the common drinking water contaminants."

Surface water in reservoirs, streams, lakes and rivers makes up only 4 percent of the fresh water in the United States. The rest is goundwater, held in underground reservoirs or aquifers.

Until the 1970s many experts believed groundwater was immune to pollution because of the depth of the aquifers.

"But since the 1950s, many underground tanks designed to store toxic chemicals have corroded, releasing enormous quantities of pollutants into the soil," King said.

"Those chemicals percolate into the aquifers. It takes only a little groundwater pollution to contaminate a larger water supply. A leak of a single gallon of gasoline a day can make well water for a community of 50,000 undrinkable for years."

More than 60,00 toxic substances are now used by U.S. manufacturing and mining industries. In addition, carcinogenic pesticides used on many food crops have contaminated thousands of water wells.

Some pollutants come from natural sources. Water flowing over arsenic, which occurs naturally in certain minerals, can pick up this poison. Radon is another natural pollutant which in some circumstances can enter the drinking water.

Infectious disease-bearing germs also can pollute water. Despite great advances in water treatment, micro-organisms still pose a threat.

Congress recently required the EPA to set new standards for chlorination and filtration to reduce contamination by infectious diseases.

Even if water is perfectly safe to drink when it leaves the treatment plant, it can become contaminated by lead in water pipes.

Briskin estimates 42 million Americans receive lead-contaminated water.

"More than 100,000 children may be suffering neurological and developmental problems; because of lead in their water," she said. "For example, lead consumption can cause learning impairment.

"The latest research shows that even very low levels of lead ingested during pregnancy are associated with premature birth, slow mental and nervous system development and shorter stature."

The only way to know for certain what's in your water is to have it tested at the tap. Check your local telephone directory to find a water-testing lab.