Senate President Thomas V. Mike Miller and House Speaker Michael E. Busch said they expect the General Assembly to pass during this session some form of the "Four Pollutants" bill, renamed the Healthy Air Act. The legislation would require coal-fired power plants to install equipment that would limit mercury and other pollution.

The Sun reported last month that Constellation Energy Corp. had worked behind the scenes with former company officials now at the Maryland Department of the Environment to derail the pollution legislation last spring.

Internal e-mails obtained through the Public Information Act showed that state Environment Secretary Kendl P. Philbrick had signed a letter to legislators arguing against the bill, using a text supplied by Constellation's lobbyist.

Constellation is the largest owner of power plants in Maryland. The company and others in the industry argue that stricter state- level air regulations would be ineffective because much of the air pollution in Maryland blows in from the Midwest.

"Constellation Energy's position remains that national and regional approaches are far more effective than state by state approaches for addressing air pollution," said Rob Gould, a company spokesman.

The chief sponsors of the Healthy Air Act, Sen. Paul G. Pinsky and Del. James W. Hubbard, both Democrats from Prince George's County, held a news conference in Annapolis Thursday with several environmental and health groups to promote the legislation.

Maryland Public Interest Research Group released a report showing that the Baltimore area ranks ninth-worst in the nation for soot pollution, down from 12th worst in 2003.

Pinsky and Hubbard said their bill would require the state's seven largest coal-fired power plants to cut sulfur dioxide pollution 83 percent by 2010, mercury 90 percent by 2010, nitrogen oxide 80 percent by 2015 and carbon dioxide 10 percent by 2018.

After opposing the air pollution bill last year, the Ehrlich administration released proposed regulations this month designed to reduce sulfur dioxide pollution by 85 percent, mercury pollution by 80 percent and nitrogen oxide pollution by 69 percent, all by 2010.

The draft rules would not cover as many power plants as the Healthy Air Act would and would allow the state to exempt about half of the plants from some of the limits, though state officials have since said they might drop the exemption language. The rules would not reduce carbon dioxide, which is thought to cause global warming and sea-level rise.

Busch said Thursday that he wants an air pollution law "more expansive than the governor's proposal."