THURSDAY, March 16 (HealthDay News) -- Reductions in fine particulate air pollution (PM2.5) are associated with lower risks of mortality from cardiovascular and respiratory disease, according to a study in the March 15 issue of the American Journal of Respiratory and Critical Care Medicine.
Francine Laden, Sc.D., of Channing Laboratory in Boston, and colleagues extended the Harvard Six Cities study from 1990 to 1998 to examine the impact of reduced PM2.5 on mortality rates. The study covered Watertown, Mass.; Kingston and Harriman, Tenn.; St. Louis, Mo.; Steubenville, Ohio; Portage, Wyocena and Pardeeville, Wis.; and Topeka, Kan.
Exposure to long-term, ambient PM2.5 had been shown by the original study to be associated with acute and chronic mortality, and the continuation of the study confirmed a positive association with total, cardiovascular and lung cancer mortality.
From 1990 to 1998, the mean concentration of PM2.5 declined 7 micrograms per cubic meter of air per decade in Steubenville, 5 μg/m3 in St. Louis, 3 μg/m3 in Watertown, 2 μg/m3 in Harriman, 1 μg/m3 in Portage and less than 1 μg/m3 in Topeka.
"City-specific average PM2.5 levels were lower in the extended follow-up during the 1990s than in the first follow-up (1974-1989) and mortality risk ratios in this period also were lower. This suggests that the PM2.5-associated mortality in this 25-year follow-up was at least, in part, reversible," the authors conclude.
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