Drinking water in the metropolitan area meets federal standards but still contains "potentially health-threatening levels" of certain chemicals, a new study concludes.

The results are similar to those of a Washington Post survey of drinking water published in the Health section in January.

Conducted by the U.S. Public Interest Research Group (U.S.-PIRG), a nonprofit lobbying group, the new study examined 1984 and 1985 records of regular chemical testing performed by local water utilities -- a requirment of the federal Safe Drinking Water Act.

Among the findings:

*All/local water utilities test for contaminants more frequently than required by the Safe Water Act. Testing for bacteria is the most common test performed.

*The number of chemicals tested for ranges from 49 in much of Virginia to 51 in Montgomery and Prince George's counties to 52 in the District. Alexandria tests for "as many as 150 chemicals," and Fairfax County tests for about 100.

*"Potentially health-threatening" levels of trihalomethanes, chemicals that form as a byproduct of chlorination, were detected throughout the region. The standard for trihalomethanes is 100 micrograms per liter. U.S.-PIRG defined as "potentially health-threatening" concentrations of trihalomethanes that exceed 50 micrograms per liter. These levels were measured by the water utilities at Dalecarlia and McMillan Water Treatment plants in the District; at the Patuxent River and the Potomac River Treatment Plants in Prince George's and Montgomery counties; in Fairfax City; Alexandria; Fairfax and Arlington counties; and the cities of Falls Church and Vienna.

*Three violations of the Safe Drinking Water Act occurred -- in September and October 1984 and August 1985 -- in Alexandria's drinking water. The water utility in Alexandria found excess bacteria and notified the public within two weeks through television, radio and newspaper press releases. In 1984, the problem was corrected by the end of October, sand in 1985 within one week of discovery.

"The violations of the bacteriological standard in Alexandria and the widespread problems with potentially health-threatening levels of trihalomethanes indicate that more needs to be done to ensure a safe water supply to all Washington area citizens," the study reports.