Particulate Air Pollution Needs to Be Controlled to Protect Public Health

Researchers at the Johns Hopkins School of Public Health have found that in spite of improved efforts to control air pollution, pollution by microscopic particles continues to be associated with adverse health effects on the public-at-large. Results of the study are published in the December 14, 2000 issue of the New England Journal of Medicine.

Recent studies showing that current levels of air pollution are associated with increased mortality and morbidity have raised concern that air pollution still poses a threat to public health. The evidence has specifically suggested that airborne particles are the toxic component of urban air pollution. In the present study, researchers examined whether a link in fact did exist between airborne particulate matter and the risk of dying.

Using a powerful analytic approach that pools evidence from multiple locations, the researchers assessed the effects of five major outdoor pollutants, including particulate matter, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide, on daily mortality in 20 of the largest cities in the United States, from 1987-1994. The populations considered in the study totaled more than 50 million.

After excluding deaths from external causes, as well as those people not permanent residents of a given city, the researchers classified deaths by age group (under 65, 65-74 years, and 75 years and older) and by cause. Results of the study consistently indicated that air pollution with particulate matter is associated with both total deaths and cardiorespiratory mortality, even after controlling for weather and other pollutants. The effect, they said, was not likely to be due to chance, and it was greater for cardiorespiratory mortality. There was also evidence, although not statistically significant, that ozone increased mortality during the summer but not in the winter. The other pollutants studied were not associated with mortality.

The researchers concluded that sufficient evidence exists that air pollution with particles is adversely affecting the public's health and that this finding strengthens the rationale for limiting concentrations of respirable particles in outdoor air.

Support for this study was provided by the Health Effects Institute, the Rosenblith Young Investigator Award from the Health Effects Institute, and the National Institute of Environmental Health Sciences for The Johns Hopkins Center in Urban Environmental Health.