Francesca Dominici

Pollution Fallout not so Fine for Health

By Mary Beth Regan

Since passage of the Clean Air Act in 1970, the nation has struggled with how to protect citizens from the dangers of dirty air. Bloomberg School researchers brought together by Epidemiologychair Jonathan M. Samet and Biostatistics chair Scott Zeger have spent the last decade piecing together data that paint a troubling picture of the impact of air pollution on human health. 

Now, a new study led by Francesca Dominici, PhD, associate professor of Biostatistics, has found a surprisingly strong association between fine particle air pollution and hospitalizations among the elderly across the entire country. These particles, coming from cars, power plants, dust fields and other sources, have long been suspected of posing health risks. 

The study, which appeared in the March 8 issue of JAMA, is notable because of its breadth. The three-year effort is the first to uncover associations by linking data on hospital admissions with pollution and weather data. In all, the study examined hospital admission records for 11.5 million elderly Americans, living within 5.9 miles of a pollution monitoring station, in 204 U.S. counties. Data were analyzed from 1999 through 2002. 

"We had to harness tremendous computing power to merge these databases," says Roger D. Peng, PhD, study co-author and an assistant professor of Biostatistics.

The team's findings: On days when tiny particle levels are higher, more elderly are admitted to the hospital for cardiovascular and respiratory ailments. For example, when fine particulate pollution was increased by 10 micrograms per cubic meter, there was a 1.28 percent increase in hospital admissions for heart failure. That means that among the 250,000 elderly people hospitalized nationwide each year for heart failure, 3,000 hospitalizations are due to higher levels of air pollution, the researchers say. 

"I was not surprised that we saw an association," says Dominici, "but I was surprised that we found an association so high."

In all, the recent study found that an increase of fine particles by 10 micrograms per cubic meter could result in at least 11,000 additional hospitalizations each year, for the diseases surveyed. Cook County, which includes Chicago, has an annual average fine particle level of 16 micrograms per cubic meter and a high level of 56 micrograms per cubic meter. On days with the highest fine particle levels, the study results predicted five extra hospital admissions for each 100 hospital admissions.

These results come amid a ferocious debate about how the nation should regulate fine particle matter. The particles measure only 1/30th the diameter of human hair, but they can be deadly because they lodge deep within the tissues of the respiratory system.

The Environmental Protection Agency is under a court order to issue final standards for this pollutant by September 27.