Lead author Andrew Correia, a Ph.D. candidate in the Department of Biostatistics at the Harvard School of Public Health, and colleagues said it is the largest study to date to find beneficial effects to public health of continuing to reduce air pollution levels in the United States.
"Despite the fact that the U.S. population as a whole is exposed to much lower levels of air pollution than 30 years ago -- because of great strides made to reduce people's exposure -- it appears that further reductions in air pollution levels would continue to benefit public health," Correia said in a statement.
The study looked at the effects of fine particulate matter, small particles of 2.5 micrometers or less in diameter. Air pollution has been declining steadily in the U.S. since 1980, but the rate has slowed in the years since 2000. The researchers found smaller decreases in small particle levels since 2000 still improved life expectancy.
After controlling for socioeconomic status, smoking prevalence and demographic characteristics, the study, published in the journal Epidemiology, found a decrease of 10 micrograms per cubic meter in the concentration of small particles of 2.5 micrometers or less in diameter from 2000 to 2007 was associated with an average increase in life expectancy of 0.35 years in 545 U.S. counties.
"The study provides strong and compelling evidence that continuing to reduce ambient levels of of small particles prolongs life," said senior author Francesca Dominici, a professor of biostatistics at Harvard School of Public Health.