Fine particulate matter composition and mortality: a multi-country multi-city analysis

Abstract

Background/Aim: Literature suggests that inter-regional variation in short-term associations between fine particulate air pollution (PM2.5) and mortality can be attributed to differences in particulate composition. However, empirical evidence is still limited. In this contribution, we used data from a multi-country study to evaluate how the associated short-term mortality risks varied depending on the average composition of PM2.5.Methods: We collected mortality, PM2.5, and weather data for 280 cities within 19 countries in 1985-2015 from the MCC Collaborative Research Network. Average composition of the PM2.5 fractions, namely black carbon (BC); sulfate (SO42-); ammonium (NH4+); nitrate (NO3-); organic matter (OM); sea salt (SS); and mineral dust (DUST), were obtained from the Atmospheric Composition Analysis Group. We applied a two-stage time-series analytic approach. First, for each city we modelled the linear associations of two-day moving average PM2.5 with total mortality using quasi-Poisson regression and distributed lag models. Second, we used multilevel meta-regression models to pool the city-specific estimates and evaluate the effect modification of each components. Results: In preliminary analyses, the percentage excess risk for mortality associated with a 10 μg/m3 increase in PM2.5 concentration was 0.57% (95%CI:0.26% to 0.87%) on average. We found significant increases in the mortality risk for an (interquartile range) IQR increase in the components for BC (0.24% to 0.51%, p<0.001) and NH4+ (0.04% to 0.43%, p=0.016), while cities with a higher percentage of sea salt have a lower percent mortality change (0.34% to 0.10%, p<0.001).Conclusion: This represents the largest study assessing effect modification in short-term mortality risks by composition of PM2.5, performed by comparing different populations across the world. Preliminary findings suggest that larger PM-mortality risks are linked to anthropogenic sources of fine particulate matter. Further steps will consider multi-components models to disentangle the effect of each component.On behalf of the MCC Collaborative Research Network