Mortality and hospitalizations due to cardiovascular and respiratory diseases associated with air pollution in Iran: A systematic review and meta-analysis

Abstract Air pollution is a major environmental health problem around the world. The purpose of this study was to investigate the relationship between exposure to air pollution with mortality and hospitalizations by conducting a systematic review and meta-analysis. Several databases were searched for studies exploring the relationship between air pollution and the all-cause, cardiovascular and respiratory mortality, as well as hospitalizations. The risk of bias assessed by the Office of Health Assessment and Translation (OHAT) Method for each study included. Random-effects model was applied to estimate the relative risks of all-cause mortality and mortality/hospitalization due to cardiovascular and respiratory diseases. We found a 0.6% (95% CI 0.5%–0.7%) increase in all-cause, 0.5% (95% CI 0.4%–0.6%) increase in cardiovascular, and 0.8% (95% CI 0.6%–0.9%) increase in respiratory mortality per 10 μg/m3 increase of pooled all air pollutants. Moreover, we observed a 0.7% (95% CI 0.6%–0.9%) increase in hospitalization due to cardiovascular and respiratory diseases per 10 μg/m3 increase of pooled air pollutants. The highest all-cause mortality was associated with exposure to particulates with aerodynamic diameters less than 2.5 μm (PM2.5) (681 deaths or 1.5%, 95% CI 1.3%–1.7%), followed by PM10 (253 deaths or 0.7%, 95% CI 0.6%–0.8%). The current study illustrated that all investigated air pollutants were associated with elevated mortality and hospitalization, but the effects of PM2.5 and PM10 were stronger. Thus, authorities need to pay more attention to establishing the new regulations to apply control measures. Systematic review registration PROSPERO: CRD42018088770