The combined effect of air pollution and temperature on respiratory health outcomes: a systematic review

Abstract

<b>Background:</b> Respiratory diseases are a leading cause of mortality and morbidity, and are exacerbated by both, air pollution and temperature. <b>Aims:</b> To assess published literature on the combined effect between short-term air pollution and temperature exposure on respiratory mortality and hospital admissions. <b>Methods:</b> We identified 26441 papers in PubMed, up to March 2020, and selected 48 for analysis; inclusion criteria included English language, observational studies, and short-term air pollution exposure. Qualitative and quantitative analysis, specifically a meta-analysis, was performed. <b>Results:</b> For respiratory mortality we found an effect of PM during warm temperature days with a meta-RR (95% CI) of 1.013 (1.003-1.023) per 10µg/m3; additionally, we found an effect of O3 during the warm season with a meta-RR of 1.006 (1.001-1.012) per 10µg/m3. For hospital admissions, we found an effect of PM10 during the warm season with a meta-RR of 1.015 (1.009-1.021) per 10µg/m3. In both our quantitative and qualitative analysis, results for cold temperatures were inconsistent. <b>Conclusions:</b> Exposure to warm temperatures and air pollution is likely to affect respiratory mortality and hospital admissions, but overall the results on the combined effect between air pollution and temperature are largely inconsistent. The interaction analysis of air pollution and temperature is a relatively new field and to date many studies do not report the interaction effect itself, but the combined magnitude of main and interaction effect in temperature strata. Future research should focus on drawing a more global conclusion on the combined effects of air pollution and temperature.