Air pollution mortality: harvesting and loss of life expectancy.

This article concerns the interpretation of epidemiological studies of air pollution mortality and the choice of indicators for quantifying the impact, for communication with policymakers. It is shown that the total mortality impact (measured by cohort studies) can only be quantified in terms of loss of life expectancy (LLE), not number of premature deaths. Time-series (TS) studies of mortality observe only acute impacts, that is, deaths due to short-term exposure ("acute mortality"); they allow the estimation of a number of deaths without providing any information on the LLE per death. However, even if the average loss per death is as long as 6 mo, acute mortality is only a very small percentage of the total mortality attributable to air pollution. Estimates of the population-average LLE due to air pollution are provided, for acute mortality, total adult mortality, and infant mortality.