View article

Rationale: A large body of epidemiologic literature has found an association of increased fine particulate air pollution (PM_2.5) with acute and chronic mortality. The effect of improvements in particle exposure is less clear.

Objectives: Earlier analysis of the Harvard Six Cities adult cohort study showed an association between long-term ambient PM_2.5 and mortality between enrollment in the mid-1970s and follow-up until 1990. We extended mortality follow-up for 8 yr in a period of reduced air pollution concentrations.

Methods: Annual city-specific PM_2.5 concentrations were measured between 1979 and 1988, and estimated for later years from publicly available data. Exposure was defined as (1) city-specific mean PM_2.5 during the two follow-up periods, (2) mean PM_2.5 in the first period and change between these periods, (3) overall mean PM_2.5 across the entire follow-up, and (4) year-specific mean PM_2.5. Mortality …