Mortality effects of longer term exposures to fine particulate air pollution: review of recent epidemiological evidence.

This article evaluates the dynamic exposure-response relationship between particulate matter air pollution (PM) and mortality risk by integrating epidemiological evidence from studies that use different time scales of exposure. The evidence suggests that short-term exposure studies are observing more than just harvesting or mortality displacement. There is little evidence of short-term compensatory reduction in deaths, and estimated PM effects are generally larger for intermediate and longer term time scales of exposure. Although proximity in time matters, with most recent exposure having the largest health impact, there is evidence that the short-term exposure studies capture only a small amount of the overall health effects of long-term repeated exposure to PM. The overall epidemiological evidence suggests that adverse health effects are dependent on both exposure concentrations and length of exposure, and that long-term exposures have larger, more persistent cumulative effects than short-term exposures.