Washington ? The Bush administration proposed tougher rules Thursday to cut smog- and soot-forming chemicals from power plants in 30 states, hoping to improve air quality across the eastern half of the country.

The Environmental Protection Agency proposal would cap emissions of sulfur dioxide and smog-causing nitrogen oxide at power plants from New England to the Midwest and reduce the amount of pollution that often drifts hundreds of miles across state lines.

EPA Administrator Mike Leavitt estimated that power plant upgrades to meet the new pollution control requirements announced Thursday would cost the industry as much as $5.5 billion annually when fully put in place. The new pollution ceilings would go into effect beginning in 2015.

The regulations, aimed primarily to reduce long-distance air pollution, will help states, especially in the Northeast, to meet the more stringent federal health-based air quality standards that were issued in 1997 but until recently had been held up in litigation.

Separately on Thursday, the EPA announced that a preliminary review showed that all or parts of 534 counties in 32 states nationwide are expected to fall below the 1997 air standards for fine soot and will have to take actions to reduce pollution. A final list of counties in noncompliance will be issued in April.

A decision on whether to rate the Kansas City metro area, including Wyandotte and Johnson counties in Kansas, as a nonattainment area was deferred until next week because the EPA has just received this year’s air quality control data for the region.

Much of the microscopic soot in the air comes from sulfur dioxide released from coal-fired power plant smokestacks as well as nitrogen oxide.