Environmental activists, state officials and others lined up at public hearings yesterday to call for tougher standards on airborne soot.

Many contend that national standards proposed by the U.S. Environmental Protection Agency don't go far enough to protect older Americans and those threatened by fine particle pollution.

The EPA is revising its standards on the pollutants in response to a lawsuit filed by the American Lung Association and other groups. A final rule is expected later this year.

In its proposed standards, the EPA failed to meet recommendations from its own scientists and the independent Clean Air Scientific Advisory Committee to "address the undisputed adverse health effects" of the pollutants, said Joyce Epps, director of air quality for the Pennsylvania Department of Environmental Protection.

"We strongly urge EPA to revise its proposed rule," Ms. Epps said in testimony prepared for yesterday's hearing in Philadelphia. Other hearings were held in Chicago and San Francisco.

The microscopic particles primarily come from vehicle exhaust, power plant emissions and other operations that involve the burning of fossil fuels. The particles can travel deep into the respiratory tract, reducing lung function and worsening conditions such as asthma and bronchitis.

Kevin Stewart, director of environmental health for the American Lung Association of the Mid-Atlantic, which includes Pennsylvania, Delaware and West Virginia, noted that hundreds of deaths each year in Pittsburgh and Philadelphia are linked to the airborne pollutants.

An industry group, the American Chemistry Council, opposed tougher standards in its testimony yesterday, saying states should focus on meeting current standards.

Some areas of Western Pennsylvania have struggled to meet current guidelines, said Guillermo Cole, a spokesman for the Allegheny County Health Department. Pollution drifting in from other states has contributed to the problem.

But more stringent guidelines could prompt coal-fired power plants and other businesses to invest in cleaner technology, said Rachel Filippini, executive director of Pittsburgh-based Group Against Smog and Pollution, known as GASP.

Experts said many studies in recent years have documented the adverse health effects of airborne soot.

In an article published yesterday in the Journal of the American Medical Association, researchers said exposure to fine particle pollution significantly increases the risk of cardiovascular and respiratory disease among older people.

The four-year study of 11.5 million Medicare enrollees found that small increases in the pollutants resulted in increased hospital admissions for heart and vascular disease, heart failure, chronic obstructive pulmonary disease and respiratory infection.

The findings "underscore the need for a national air quality standard that adequately protects the respiratory health of our citizens," said Dr. Francesca Dominici, the study's lead author and an associate professor of biostatistics at the Johns Hopkins Bloomberg School of Public Health.