Air Pollution and Deaths among Elderly Residents of Sao Paulo, Brazil: An Analysis of Mortality Displacement

Background: Evaluation of short-term mortality displacement is essential to accurately estimate the impact of short-term air pollution exposure on public health. Objectives: We quantified mortality displacement by estimating single-day lag effects and cumulative effects of air pollutants on mortality using distributed lag models. Methods: We performed a daily time series of nonaccidental and cause-specific mortality among elderly residents of Sao Paulo, Brazil, between 2000 and 2011. Effects of particulate matter smaller than 10 mu m (PM10), nitrogen dioxide (NO2) and carbon monoxide (CO) were estimated in Poisson generalized additive models. Single- day lag effects of air pollutant exposure were estimated for 0-, 1- and 2- day lags. Distributed lag models with lags of 0-10, 0-20 and 0-30 days were used to assess mortality displacement and potential cumulative exposure effects. Results: PM10, NO2 and CO were significantly associated with nonaccidental and cause-specific deaths in both single-day lag and cumulative lag models. Cumulative effect estimates for 0-10 days were larger than estimates for single-day lags. Cumulative effect estimates for 0-30 days were essentially zero for nonaccidental and circulatory deaths but remained elevated for respiratory and cancer deaths. Conclusions: We found evidence of mortality displacement within 30 days for nonaccidental and circulatory deaths in elderly residents of Sao Paulo. We did not find evidence of mortality displacement within 30 days for respiratory or cancer deaths.