Short-term association between ambient air pollution and cardio-respiratory mortality in Rio de Janeiro, Brazil

Background Several epidemiological studies have reported associations between ambient air pollution and mortality. However, relatively few studies have investigated this relationship in Brazil using individual-level data. Objectives To estimate the short-term association between exposure to particulate matter <10 mu m (PM10) and ozone (O-3), and cardiovascular and respiratory mortality in Rio de Janeiro, Brazil, between 2012 and 2017. Methods We used a time-stratified case-crossover study design with individual-level mortality data. Our sample included 76,798 deaths from cardiovascular diseases and 36,071 deaths from respiratory diseases. Individual exposure to air pollutants was estimated by the inverse distance weighting method. We used data from seven monitoring stations for PM10 (24-hour mean), eight stations for O3 (8-hour max), 13 stations for air temperature (24-hour mean), and 12 humidity stations (24-hour mean). We estimated the mortality effects of PM10 and O-3 over a 3-day lag using conditional logistic regression models combined with distributed lag non-linear models. The models were adjusted for daily mean temperature and daily mean absolute humidity. Effect estimates were presented as odds ratios (OR) with their 95% confidence interval (CI) associated with a 10 mu g/m3 increase in each pollutant exposure. Results No consistent associations were observed for both pollutant and mortality outcome. The cumulative OR of PM10 exposure was 1.01 (95% CI 0.99-1.02) for respiratory mortality and 1.00 (95% CI 0.99-1.01) for cardiovascular mortality. For O-3 exposure, we also found no evidence of increased mortality for cardiovascular (OR 1.01, 95% CI 1.00-1.01) or respiratory diseases (OR 0.99, 95% CI 0.98-1.00). Our findings were similar across age and gender subgroups, and different model specifications. Conclusion We found no consistent associations between the PM10 and O-3 concentrations observed in our study and cardio-respiratory mortality. Future studies need to explore more refined exposure assessment methods to improve health risk estimates and the planning and evaluation of public health and environmental policies.