At the Food and Drug Administration building, employes can't drink from the water fountains because the water system has been contaminated with freon from a cooling system. The water foams as it flows from the faucets.

In the Occoquan Reservoir in Virginia, tests have turned up low levels of atrazine and carbofuran -- two pesticides used on corn crops.

In 1983, the Fairfax County Health Department issued an advisory to the medical society urging that doctors tell their patients on sodium-restricted diets to avoid drinking the water in Vienna. At 23 milligrams per liter, the water exceeded limits for persons on a "strict" low-sodium diet.

And perhaps most important, a recent survey of tap water in the metropolitan region by The Washington Post shows that area drinking water contains significant levels of chloroform, a cancer-causing chemical. Although the water meets the Environmental Protection Agency's (EPA) standards for chloroform, many people -- including some within the agency -- suggest that the regulation may be too lax. Since, in addition to drinking the water, people bathe in it and breathe vapors liberated during shower and bathing, it is feared that the risk may be higher than EPA had considered.

"Chloroform is a very, very volatile chemical," said David Burmaster, an engineer and former staff member of the President's Council on Environmental Quality during the Carter administration. "When you take a shower, chloroform will spray out of the water."

Heat in the shower changes chloroform in the water to a gas, which is then inhaled. Doing dishes or washing clothes releases additional chloroform into the air, where it hangs, Burmaster said, waiting to be inhaled -- particularly when windows and doors are kept shut.

Soaking in a bath may increase the exposure. Chloroform "penetrates the skin," Burmaster said, "and gets into the bloodstream."

"EPA," he said, "doesn't count that exposure. EPA assumed that the only pathway of exposure was through the gut."

"At the time we set the original consideration of standards for chloroform and other related chemicals known collectively as trihalomethanes , we did not take those routes of exposure into account," said Arnold Kuzmack, acting deputy director for EPA's Office of Drinking Water. "Skin exposure to chloroform is little. Inhalation may be more . . .

"We have become more concerned with the inhalation exposure from volatile chemicals in the water, particularly for the shower. We've done some rough calculations which suggest that risk of exposure from taking a shower is roughly equivalent to the exposure from drinking two liters of water a day.

"It may well be, with the experience that we've had now, that we may decide the standard for chloroform and other trihalomethanes could go lower."

EPA considers the technical feasibility of limiting chemicals in water and in general allows a level that could produce at most one case of cancer in 1 million people over their lifetimes.

But for calculating the standard for trihalomethanes, EPA uses a risk of one in 10,000 people developing cancer from exposure. Chlorine's role in fighting diseases like typhoid is the justification for this more lenient standard.

The bottom line is that water in Washington, like the water in many large cities throughout the country, "meets federal drinking water standards," Burmaster said. "But with the chloroform levels up where they are, it's not pristine water.

"Is it great water? No."

Is it water that's going to cause cases of cancer or other illness?

"There is no safe exposure to some of these contaminants," said Jon Hutchison, an environmental planner and former professor at the University of Virginia. "The higher the level, the greater number of people who will come down with cancer. I have a lot of concern about cleaning up all the water in the metropolitan area. I can't understand why states and communities don't give stronger powers to protect safe drinking water."

Critics also charge that the EPA has set standards for just a handful of the thousands of potential contaminants in drinking water. At present, the agency has set standards for only 22 chemicals, although there are proposals to regulate another 20 to 25.

"We, too, are disappointed in how long it's taking to do all this stuff," said EPA's Kuzmack. "Part of the problem is that when the Safe Drinking Water Act was passed in 1974, a lot this scientific knowledge did not exist."

The Safe Drinking Water Act for the first time established federal oversight of the nation's thousands of local water systms.

On the whole, said Joseph Cotruvo, head of the EPA's Drinking Water Office, "the water quality situation is better now than it was 10 years ago, before there was a national regulation."

"I drink the water in Washington," Kuzmack said. "My family drinks it. Certainly in larger systems, which are professionally run, the vast majority of water is very very professionally handled. As we learn more and more about these exotic chemicals, we will learn more about what we have to deal with."

A century ago, Americans took their chances when they poured a glass of water. In Washington, for instance, water flowed, as it does today, from the Potomac into the Dalecarlia and the Georgetown reservoirs. Sediment was filtered out, but not much else. There were reports that an occasional eel flowed through kitchen faucets.

When chlorination was introduced in the 1920s, it was considered a wonder chemical, much like penicillin came to be a wonder drug a few decades later. Chlorine was able to disinfect water, and for the first time help control the spread of numerous water-borne diseases, including typhoid and cholera.

With chlorination, water utilities thought they had the answer to safe water. It would be another 50 years before EPA scientists discovered that chlorine use had a tradeoff: the greater the amount of chlorine, the higher the concentrations of trihalomethanes -- chemical byproducts of the chlorination process, including the carcinogen chloroform.

Then came the age of pesticides and herbicides in the 1950s and '60s, and by the '70s increasing numbers of contaminants were showing up in the water.

The result: More and more people are asking, "Is the drinking water really safe?" This concern echoes nationwide, in small towns and in large cities alike.

It's being asked in Florida, where a 1982 EPA study of well water found some of the highest levels of trihalomethanes, including chloroform.

It's being asked in San Jose, Calif., where TCA (the chemical solvent 1,1,1-trichloroethane) leaked into a well supplying drinking water to nearby industrial and residential areas.

It's being asked in Rhode Island, where more than a third of wells had nitrate levels exceeding EPA's 10-milligram-per-liter limit.

It's being asked at the FDA building on C Street in Southwest Washington, where refrigeration coils failed this fall and contaminated the water with the chemical freon, leaving the water effervescent as it came from drinking fountains. The problem persists.

Increasingly, whether the question is asked about individual wells or public water systems, the answer is uncertain.

"I don't think that we do know what's really in the water," said Jacqueline Warren, an attorney and advocate of safe drinking water for the Natural Resources Defense Council, a nonprofit lobbying group. "A lot of contamination has been found, and routine monitoring doesn't cover many of the contaminants. I don't think that anyone can really make a judgment that the water is safe right now."

And as for turning to bottled water, Warren said people should think twice.

"The contaminants that people think they are avoiding by drinking bottled water may not be avoided," she said. "It costs 1,000 times more for bottled water, and you're not necessarily getting anything better, and may, in fact, be drinking something that's not even as good as tap water."

Neither is there cause "for hysteria and panic," said Velma Smith, director of the Groundwater and Drinking Water Protection Project at the Environmental Policy Institute, another environmental group that lobbies for safe tap water. "The water utilities do a good job of providing us with good, clean water today. But if you look at the long-term effects, the question is, in our growing dependence on chemicals, are we jeopardizing our drinking water supply? I don't think that we have the measure to say if the water's safe for the long term." In the United States there are an estimated 60,000 community water systems supplying drinking water to some 200 million Americans. EPA's current 22 regulations range from one that sets the optimum level for bacteria in the water to others that govern how much arsenic, mercury, lead and other substances may be present.

Balanced against those 22 standards are more than 60,000 organic chemicals for which there are no drinking water contamination regulations. Some of those chemicals are stored underground. Others run off corn fields and driveways and slowly seep down into the earth, where they mingle with the ground water in wells used to supply homes and cities.

Some chemicals are dumped deliberately as waste products into streams and rivers. Others are part of the industrial and agricultural runoff flowing into rivers such as the Potomac and the Patuxent -- two of the major sources of drinking water in the Washington area.

Given these vast numbers of potential contaminants, "the sort of yardstick that we're using to see whether water is potable or not is just way out of date," said Smith, the Environmental Policy Institute lobbyist. "It's antiquated."

Take the Occoquan Reservoir, for instance -- source of two thirds of the drinking water for residents served by the Fairfax County Water Authority. In a special pilot program developed in 1982 by Fairfax as an early warning system for chemicals that could enter the water system, almost half of the 48 chemicals turned up. While the vast majority have been in raw, untreated water, a few, like the plasticizers dioctyl phthalate and butyl benzyl phthalate, are appearing in small amounts in finished water. The EPA says pthalates do not cause cancer but can be toxic in high doses.

Evidence suggests that the Occoquan experience is not an isolated one.

In a recent EPA survey, 28 percent of wells in metropolitan regions were contaminated by at least trace amounts of one or more toxic organic chemicals. Another survey showed that 63 percent of rural water supplies were also contaminated. And Smith notes that every state in the union has now reported chemical contamination of well waters -- the source of drinking water for more than half of all Americans today.

Similar contaminants are showing up in surface waters -- the streams and rivers that supply many metropolitan regions, including Washington, with drinking water.

This week, when Congress goes back into session, one of the first tasks lawmakers are expected to tackle is a reauthorization of the Safe Drinking Water Act. Last year, both the House and Senate passed bills to revise the act, with more stringent standards and greater enforcement powers for the EPA. Congress now will attempt to resolve technical differences between the bills before they go to the president.

"The new law, I think, is going to push us along and help us by leaps and bounds, but we have a long way to go," said Smith. "We're going to have to push EPA and say we just can't keep looking at these same 22 chemicals. And the utilities are going to see that this law is for them to obey, not ignore."

The effect of budget constraints on the EPA's activities is unknown.

"The uncertainty is the whole Gramm-Rudman bill," said Smith. "The Drinking Water Office budget hasn't fared very well in the past. Unless they're going to have the money to do those things, I don't know how much [EPA] will be able to do."

*The bigger question facing the country, experts say, is how bad are we willing to let the drinking water get? The only sure way to guarantee safe drinking water is to protect the original source of water, said Daniel Okun, professor of environmental engineering at the University of North Carolina. "Depending on monitoring and treating water is a defensive procedure, and a misguided approach," he said. "It is not as important as selection of a source of water that is free of contamination."

The idea that chemicals and other contaminants can continue to be removed through filtration and other treatment -- no matter what the levels -- does not appear to be true, he contends.

"The effect of these chemical contaminants doesn't show up for several decades," Okun said. "It's like the asbestos problem. It's difficult to trace. That's why using the highest-quality water source is so important."

More water utilities, he believes, will have to follow New York City's lead. More than a hundred years ago, Okun said, people thought New York officials were being extravagant when they decided to buy land surrounding the city's water sources in upstate New York. But that foresight, Okun said, is what keeps New York City water among the best in the country.

Experts also say that the public must decide how much it is willing to pay for clean, contaminant-free water. Drinking water today is one of the best buys left, costing just pennies per gallon. The EPA estimates it could cost about $50 a year per household to improve the treatment now used for purifying water. This would include implementing some of the more expensive treatments -- such as ozone purification now used in France and several other European countries to supplement chlorine.

Despite the problems, most experts agree that picture does not have to be all doom and gloom.

"I've been working in the water field since 1973," said Warren. "I've seen a lot of changes, and I'm optimistic that there will be more."