Particle pollution said to boost risk of death

March 10, 1995|By Timothy B. Wheeler | Timothy B. Wheeler,Sun Staff Writer

A major new study finds that people living in polluted American cities like Baltimore have a significantly higher risk of death from breathing air laden with tiny soot particles.

The research, which tracked more than 500,000 people in Baltimore and 150 other U.S. urban areas, found that residents of the most polluted cities had a 15 percent to 17 percent higher risk of death from lung cancer or from heart or lung disease than did those in the least polluted communities.

The study, reported in this month's American Journal of Respiratory and Critical Care Medicine, is the largest of its kind. Conducted by researchers at the Harvard School of Public Health, Brigham Young University and the American Cancer Society, it expands on a study two years ago that linked particle pollution with increased deaths in six of the largest U.S. cities.

"The danger is not just in Los Angeles or New York," said Douglas Dockery, professor of environmental epidemiology at Harvard, and one of the study's co-authors. For the Baltimore area, which had neither the most nor the least pollution, he said the study suggests that residents may be shortening their lives by "a year or so."

Previous research had suggested that particle pollution may cause as many as 50,000 deaths a year nationwide. Researchers suspect that the most likely victims are children and adults with serious respiratory or heart ailments. But Dr. Dockery noted that lifelong exposure to particle-laden air may be the cause for the heightened risk of lung cancer found in the latest study.

Investigators followed 552,138 adults in 151 urban areas from 1982 through December 1989, and compared the deaths in each city with local air pollution levels, which are monitored regularly and reported to the federal government. The statistics were adjusted to account for smoking, education and other factors affecting individuals' risks.

The increased risk of early death from particle pollution seems small compared with the hazards of cigarettes, which can shorten a smoker's life by 10 years, Dr. Dockery said. But the research raises new concerns about a form of air pollution that many believed had been largely reduced to acceptable levels.

Most federal and state air pollution control efforts in recent years have been directed at reducing ground-level ozone, commonly known as smog. But Dr. Dockery suggested that some of that focus may be misdirected.

"Ozone clearly has health effects at current levels," he said. The Baltimore area has the sixth-highest ozone level among U.S. cities, according to the Environmental Protection Agency. Ozone causes lung inflammation, eye irritation and breathing difficulties.

But Dr. Dockery said, "We think some of the health effects associated with summer ozone are due in part to particles." Indeed, the whitish haze over cities in summer often labeled as smog really is fine airborne particles, not ozone, which is invisible.

Particulate pollution in most of the cities studied, including Baltimore, is below the limit set by the EPA. But the agency, prompted by earlier research suggesting that soot and smoke at legal levels may still pose health risks, has launched a scientific review of its particulate pollution standards.

Should the EPA decide to tighten the particulate air pollution standard, it could be costly. Fine particles come from a wide variety of sources, including cigarettes, road dust and soot from burning fossil fuels in power plants, diesel buses and trucks, wood stoves, and gasoline-powered cars and vans.

"It's a multibillion-dollar issue, and one that deserves our best possible attention," said Roger McClellan, president of the Chemical Industry Institute of Toxicology. He called for more research before costly new pollution controls are required.

Although this and other epidemiological studies have found links between air pollution and death and heart and lung ailments, laboratory researchers have been unable to produce similar health effects in animals at the low-level exposures that are common in the air of most cities.

Nor have scientists been able to pinpoint the types of particles that cause damage to lung tissue and impair health. Increased mortality was found in cities where particle pollution was generated by a differing mix of sources.

"A particle in the East is not the same as a particle in Utah," Dr. Dockery said.

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