Los Angeles Times

Dust and soot in the air contribute to between 20 and 200 early deaths each day in America’s biggest cities, including Seattle, according to the largest coast-to-coast scientific study of the problem.

Ill health from particulates — tiny specks smaller than the width of a human hair — is spread across 20 of the largest cities in the United States, the new research indicates. Elderly people suffer the most harm.

For years, researchers have known that microscopic particles can lodge deep in the lungs. They have known, as well, that high levels of particles in the air are associated with respiratory illness, heart attacks and premature deaths.

But whether or not the particles are the cause of illness has been in dispute. The Environmental Protection Agency has been attempting to tighten rules that limit emissions of particles. Critics in the business community are challenging those new rules in the Supreme Court, arguing that the regulations are too costly and that the scientific evidence behind them is too sketchy.

The new study, conducted by a team of researchers at Johns Hopkins University in Maryland and published in the current edition of the New England Journal of Medicine, is likely to bolster the EPA’s case. The researchers found strong evidence that dust and soot particles, and not other factors suggested by industry, appear to be causing the harmful effects. And they found that ill effects occur even in cities that meet existing national air pollution standards, suggesting that stronger controls would protect public health.

The researchers examined daily changes in air pollution and mortality between 1987 and 1994 and made allowance for other factors that could skew the results, including access to health care, influenza outbreaks, socioeconomic status, weather and the presence of other pollutants.

"When we look nationally, we see an effect of particles on mortality that suggests there is a public health problem. The science continues to indict particles and their role in mortality," said Dr. Jonathan Samet, lead author of the study and chairman of the epidemiology department at Johns Hopkins University.

The metropolitan areas included in the study were:

Seattle, New York, Los Angeles, Santa Ana-Anaheim, San Bernardino, San Diego, San Jose, Oakland, Philadelphia, Pittsburgh, Atlanta, Miami, Cleveland, Detroit, Chicago, Minneapolis, Dallas-Forth Worth, Houston, San Antonio and Phoenix.