Browsing by Author "Burnett, Richard T."
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- Air pollution mixture complexity and its effect on PM2.5-related mortality: A multicountry time-series study in 264 citiesPublication . Masselot, Pierre; Kan, Haidong; Kharol, Shailesh K; Bell, Michelle L.; Sera, Francesco; Lavigne, Eric; Breitner, Susanne; das Neves Pereira da Silva, Susana; Burnett, Richard T.; Gasparrini, Antonio; Brook, Jeffrey R.; MCC Collaborative Research NetworkBackground: Fine particulate matter (PM2.5) occurs within a mixture of other pollutant gases that interact and impact its composition and toxicity. To characterize the local toxicity of PM2.5, it is useful to have an index that accounts for the whole pollutant mix, including gaseous pollutants. We consider a recently proposed pollutant mixture complexity index (PMCI) to evaluate to which extent it relates to PM2.5 toxicity. Methods: The PMCI is constructed as an index spanning seven different pollutants, relative to the PM2.5 levels. We consider a standard two-stage analysis using data from 264 cities in the Northern Hemisphere. The first stage estimates the city-specific relative risks between daily PM2.5 and all-cause mortality, which are then pooled into a second-stage meta-regression model with which we estimate the effect modification from the PMCI. Results: We estimate a relative excess risk of 1.0042 (95% confidence interval: 1.0023, 1.0061) for an interquartile range increase (from 1.09 to 1.95) of the PMCI. The PMCI predicts a substantial part of within-country relative risk heterogeneity with much less between-country heterogeneity explained. The Akaike information criterion and Bayesian information criterion of the main model are lower than those of alternative meta-regression models considering the oxidative capacity of PM2.5 or its composition. Conclusions: The PMCI represents an efficient and simple predictor of local PM2.5-related mortality, providing evidence that PM2.5 toxicity depends on the surrounding gaseous pollutant mix. With the advent of remote sensing for pollutants, the PMCI can provide a useful index to track air quality.
- Differential Mortality Risks Associated With PM2.5 Components: A Multi-Country, Multi-City StudyPublication . Masselot, Pierre; Sera, Francesco; Schneider, Rochelle; Kan, Haidong; Lavigne, Éric; Stafoggia, Massimo; Tobias, Aurelio; Chen, Hong; Burnett, Richard T.; Schwartz, Joel; Zanobetti, Antonella; Bell, Michelle L.; Chen, Bing-Yu; Guo, Yue-Liang Leon; Ragettli, Martina S.; Vicedo-Cabrera, Ana Maria; Åström, Christofer; Forsberg, Bertil; Íñiguez, Carmen; Garland, Rebecca M.; Scovronick, Noah; Madureira, Joana; Nunes, Baltazar; De la Cruz Valencia, César; Hurtado Diaz, Magali; Honda, Yasushi; Hashizume, Masahiro; Ng, Chris Fook Cheng; Samoli, Evangelia; Katsouyanni, Klea; Schneider, Alexandra; Breitner, Susanne; Ryti, Niilo R.I.; Jaakkola, Jouni J.K.; Maasikmets, Marek; Orru, Hans; Guo, Yuming; Valdés Ortega, Nicolás; Matus Correa, Patricia; Tong, Shilu; Gasparrini, AntonioBackground: The association between fine particulate matter (PM2.5) and mortality widely differs between as well as within countries. Differences in PM2.5 composition can play a role in modifying the effect estimates, but there is little evidence about which components have higher impacts on mortality. Methods: We applied a 2-stage analysis on data collected from 210 locations in 16 countries. In the first stage, we estimated location-specific relative risks (RR) for mortality associated with daily total PM2.5 through time series regression analysis. We then pooled these estimates in a meta-regression model that included city-specific logratio-transformed proportions of seven PM2.5 components as well as meta-predictors derived from city-specific socio-economic and environmental indicators. Results: We found associations between RR and several PM2.5 components. Increasing the ammonium (NH4+) proportion from 1% to 22%, while keeping a relative average proportion of other components, increased the RR from 1.0063 (95% confidence interval [95% CI] = 1.0030, 1.0097) to 1.0102 (95% CI = 1.0070, 1.0135). Conversely, an increase in nitrate (NO3-) from 1% to 71% resulted in a reduced RR, from 1.0100 (95% CI = 1.0067, 1.0133) to 1.0037 (95% CI = 0.9998, 1.0077). Differences in composition explained a substantial part of the heterogeneity in PM2.5 risk. Conclusions: These findings contribute to the identification of more hazardous emission sources. Further work is needed to understand the health impacts of PM2.5 components and sources given the overlapping sources and correlations among many components.