Study Finds Airborne Grit Can Be Fatal

The largest study ever conducted on the health effects of airborne particles from traffic and smokestacks has found that people in the nation’s most polluted cities are 15% to 17% more likely to die prematurely than those in cities with the cleanest air.

This form of pollution is killing citizens even in areas that meet Environmental Protection Agency air-quality standards, said study co-author Douglas Dockery of the Harvard School of Public Health, and “the impact on life and health is more pervasive than previously thought.”

The toll is highest in highly polluted places such as Los Angeles, Dockery said.

Overall air quality in American cities has improved dramatically since the period covered by the study, thanks in part to new federal requirements in the Clean Air Act Amendments of 1990. But the fine particles associated with increased mortality rates seen in the study are a type of pollution that is not separately regulated under the clean-air standards.

The nationwide project tracked the health histories of 552,138 adults in 151 metropolitan areas from 1982 through 1989, and compared mortality data in each location with the amount of fine particulate matter--such as soot, smoke and sulfate particles in the air--measured by the EPA at each site.

For each subject who died during the study period, cause of death was determined from death certificates. After factoring out effects of age, sex, tobacco use, occupational exposure to pollution, obesity and alcohol use, researchers found high sulfate and fine particulate levels raised the risk of premature death from all causes by 15% and 17%, respectively.

Researchers estimate that 15 or more years of exposure would be required to cause the worst health problems, and thus restricted their study to people age 30 or older.

The new findings agree with a 1993 study by many of the same authors that covered about 8,000 people in six cities.