Industrial polluters may use tall smokestacks as a partial method of meeting air-quality standards, the U.S. Court of Appeals for the District of Columbia ruled yesterday, handing the Environmental Protection Agency a significant victory in one of its longest-running legal battles.

But the three-judge panel also ruled in favor of environmental groups on two regulatory provisions that may affect as many as 200 of the nation's largest coal-fired power plants. The decision means that the EPA may have to tighten controls on those plants, which are responsible for nearly one-third of the nation's emissions of air-fouling sulfur dioxide.

The latest ruling in a lawsuit that dates back to 1970 had both sides claiming victory yesterday.

"It's a significant partial victory, but they didn't draw the line where we hoped they'd draw it," said David Hawkins of the Natural Resources Defense Council, which joined the Sierra Club in the appeal against the EPA, Kennecott Copper Corp. and the coal, paper and power industries.

EPA attorney Alan Eckert said the 63-page ruling was "a vindication of our basic approach. We're disappointed that it's not a total victory."

At issue are the soaring stacks adopted by some industries as a way of complying with air-quality standards designed to make sure air is breathable at ground level. The EPA sanctioned the use of tall stacks in 1970 and has been in court on the issue ever since.

Environmentalists contend, and the courts have generally agreed, that tall stacks have simply transferred problems elsewhere, in the form of sulfur haze and acid rain.

As a result of the rulings, the EPA has been gradually tightening the rules on tall stacks. The regulations at issue in yesterday's decision were written in 1985 on the agency's fifth try.

The decision upheld an EPA regulation granting, under a complex formula, pollution-control credit for stacks designed to prevent "downwash" pollution caused by air eddies near buildings. Environmentalists had argued that such credit could be given only after industries had rigorously controlled their emissions, but the court said it found no evidence Congress intended a "control-first strategy."

However, the court refused to accept a provision that would have given automatic credit to certain industries whose stacks were no more than 2 1/2 times taller than the nearest building that might create a "downwash." The rule was aimed at about 170 power plants that raised their stack heights before rules were tightened in 1979.

It also rejected an exemption from tall-stack regulations for certain industries using a "combined stack," whereby all emissions are piped into a single smokestack.