Visibility, air quality and daily mortality in Shanghai, China

This study was designed to assess the association between visibility and air quality, and to determine whether the variations in daily mortality were associated with fluctuations in visibility levels in Shanghai, China. Mortality data were extracted from the death certificates, provided by Shanghai Municipal Center of Disease Control and Prevention, and visibility data were obtained from Shanghai Municipal Bureau of Meteorology. Air quality data (PM₁₀, PM_2.5, PM_10-2.5, SO₂, NO₂ and O₃) were obtained from Shanghai Environmental Monitoring Center. Generalized additive model (GAM) with penalized splines was used to analyze the mortality, visibility, air pollution, and covariate data. Among various pollutants, PM_2.5 showed strongest correlation with visibility. Visibility, together with humidity, was found appropriate in predicting PM_2.5 (R-squared: 0.64) and PM₁₀ (R-squared: 0.62). Decreased visibility was significantly associated with elevated death rates from all causes and from cardiovascular disease in Shanghai; one inter-quartile range (8 km) decrease in visibility corresponded to 2.17% (95%CI: 0.46%, 3.85%), 3.36% (95%CI: 0.96%, 5.70%), and 3.02% (95%CI: - 1.32%, 7.17%) increase of total, cardiovascular and respiratory mortality, respectively. The effect estimates using predicted PM_2.5 and PM₁₀ concentrations were similar to those assessed using actual concentrations. This is the first study in Mainland China assessing the association between visibility and adverse health outcomes. Our findings suggest the possibility of using visibility as a surrogate of air quality in health research in developing countries where air pollution data might be scarce and not routinely monitored.