Temporal variations in the short-term effects of ambient air pollution on cardiovascular and respiratory mortality: a pooled analysis of 380 urban areas over a 22-year period
Maximilian Schwarz, Annette Peters, Massimo Stafoggia, Francesca de’Donato, Francesco Sera, Michelle L. Bell, Yuming Guo, Yasushi Honda, Veronika Huber, Jouni J. K. Jaakkola, Aleš Urban, Ana María Vicedo-Cabrera, Pierre Masselot, Eric Lavigne, Souzana Achilleos, Jan Kyselý, Evangelia Samoli, Masahiro Hashizume, Chris Fook Sheng Ng, Susana das Neves Pereira da Silva, Joana Madureira, Rebecca M. Garland, Aurelio Tobı́as, Ben Armstrong, Joel Schwartz, Antonio Gasparrini, Alexandra Schneider, Susanne Breitner, Haidong Kan, Samuel Osorio, Hans Orru, Ene Indermitte, Marek Maasikmets, Niilo Ryti, Mathilde Pascal, Klea Katsouyanni, Antonis Analitis, Alireza Entezari, Fatemeh Mayvaneh, Yoonhee Kim, Barrak Alahmad, Magali Hurtado Diaz, Eunice Elizabeth Félix Arellano, Shilpa Rao, Alfonso Diz-Lois Palomares, Noah Scovronick, Fiorella Acquaotta, Ho Kim, Whanhee Lee, Carmen Íñiguez, Bertil Forsberg, Martina S Ragettli, Yue Leon Guo, Shih-Chun Pan, Shanshan Li, Antonella Zanobetti
Abstract
Background Ambient air pollution, including particulate matter (such as PM 10 and PM 2·5 ) and nitrogen dioxide (NO 2 ), has been linked to increases in mortality. Whether populations' vulnerability to these pollutants has changed over time is unclear, and studies on this topic do not include multicountry analysis. We evaluated whether changes in exposure to air pollutants were associated with changes in mortality effect estimates over time. Methods We extracted cause-specific mortality and air pollution data collected between 1995 and 2016 from the Multi-Country Multi-City (MCC) Collaborative Research Network database. We applied a two-stage approach to analyse the short-term effects of NO 2 , PM 10 , and PM 2·5 on cause-specific mortality using city-specific time series regression analyses and multilevel random-effects meta-analysis. We assessed changes over time using a longitudinal meta-regression with time as a linear fixed term and explored potential sources of heterogeneity and two-pollutant models. Findings Over 21·6 million cardiovascular and 7·7 million respiratory deaths in 380 cities across 24 countries over the study period were included in the analysis. All three air pollutants showed decreasing concentrations over time. The pooled results suggested no significant temporal change in the effect estimates per unit exposure of PM 10 , PM 2·5 , or NO 2 and mortality. However, the risk of cardiovascular mortality increased from 0·37% (95% CI –0·05 to 0·80) in 1998 to 0·85% (0·55 to 1·16) in 2012 with a 10 μg/m 3 increase in PM 2·5 . Two-pollutant models generally showed similar results to single-pollutant models for PM fractions and indicated temporal differences for NO 2 . Interpretation Although air pollution levels decreased during the study period, the effect sizes per unit increase in air pollution concentration have not changed. This observation might be due to the composition, toxicity, and sources of air pollution, as well as other factors, such as socioeconomic determinants or changes in population distribution and susceptibility. Funding None.