The Environmental Protection Agency set drinking-water standards yesterday for eight dangerous chemicals in an effort to reduce the cancer threat they pose, but environmentalists criticized the standards as inadequate.

The regulations are the first for the eight volatile organic compounds, seven of which are believed to cause cancer. At least one of the eight compounds, which are used chiefly as machinery degreasers, has penetrated 20 percent of U.S. underground water supplies as a result of improper disposal on the ground, the EPA said.

About 1,800 of the nation's 79,000 public water systems, principally in industrialized areas, contain excessive levels of the chemicals, according to the EPA. No contamination by these chemicals is known in the Washington area.

The standards are expected to cut the cancer risk posed by the chemicals from a worst-case estimate today of one extra case per 1,000 exposed persons to as few as one extra case for every 1 million people, officials said. The estimates are based on the daily consumption of two quarts of polluted water for 70 years.

Lawrence J. Jensen, assistant EPA administrator for water, called the standards "stringent," saying that they will "counter" a "potentially dangerous situation."

But Jacqueline Warren, senior attorney for the Natural Resources Defense Council, said the standards are "not protective enough" and will expose consumers to an unnecessarily high risk of cancer despite technology that could further lower the risk.

The standard for the known human carcinogen vinyl chloride is expected to lower the cancer risk to one additional case per 10,000 persons exposed, which, Warren said, is still "high risk."

She said that carbon filtration systems and other water cleansing devices "can get the numbers lower."

Joseph Cotruvo, director of standards for the EPA's Office of Drinking Water, said that while technology may be able to remove more of the chemicals from drinking water than required by the regulations, it is not feasible.

"The question is: Is it practical to apply technology where there's very little to be removed?" he said.

Under the regulations effective in 18 months, water suppliers are required to monitor drinking water for the known human carcinogens vinyl chloride and benzene; the probable human carcinogens trichloroethylene, carbon tetrachloride and 1,2-dichloroethane; the possible human carcinogens para-dichlorobenzene and 1,1-dichloroethylene, and the central nervous system toxin 1,1,1-trichloroethane.

The results are to be sent to state governments, which are responsible for assuring compliance with the standards.

To comply with the standards, the 1,800 water systems with excessive levels of contamination will have to spend $22 million yearly, the EPA said.