How is cardiovascular disease mortality risk affected by duration and intensity of fine particulate matter exposure? An integration of the epidemiologic evidence

An integrated evaluation of representative epidemiological evidence provides interesting insights regarding how cardiovascular mortality risks are affected by exposure to fine particulate matter air pollution. The literature can be interpreted as indicating that cardiovascular health effects are dependent on at least two dimensions of cumulative exposure-the intensity of exposure and the duration of exposure. The empirical evidence is incomplete and there are substantial limitations related to literature-based cross-study comparisons. Nevertheless, the evidence suggests that there is a progressive approximately log reduction in the marginal increase in mortality risk for both dimensions of cumulative exposure. Longer duration exposure has larger, more persistent cumulative effects than short-term exposure, but the highest marginal effects occur with relatively short-term exposures most proximal in time. With regards to intensity of exposure, very steep, near-linear, exposure-response relationships are observed for low to moderate exposures and there is a flattening out or leveling off of the exposure-response function at very high exposures.