EPA plans to propose a regulatory change early this month that may remove the threat of federal sanctions for several localities that failed to meet the New Year's Day deadline for cleaning up their air.

About 200 counties across the country have failed to reduce their "total suspended particulates"--the technical term for dust and dirt particles emitted by refineries, steel mills and other plants--to the level required by the Clean Air Act.

But the EPA plans to revise its yardstick for measuring particles to exclude those larger than 10 microns, since the agency's science advisers have said that only the smaller particles pose health threats. The larger particles, the scientists said, are too big to penetrate the respiratory system.

Eliminating larger particles from the pollution count would allow a higher number of fine particles, EPA officials said, leaving only 20 of the 200 counties in violation of the standard.

However, that may not solve the problem of federal sanctions. Many of the counties have failed to reduce other key pollutants, such as carbon monoxide and ozone, to acceptable levels. The new particulate standard may not take effect for several months, and EPA officials said they plan to forge ahead with sanctions against areas that failed to meet national air quality standards by Dec. 31.

EPA Administrator Anne M. Gorsuch has threatened to cut off federal highway aid, clean air grants and other aid to violators.

Meanwhile, the proposal is expected to come under attack, in part because of ammunition generated by the EPA. A study by an EPA consultant found that the "societal benefit" of a stringent standard outweighs its cost.