Impacts of atmospheric environment on mortality risk among sensitive populations in Chinese megacities：A retrospective study based on long-term visibility observations

Epidemiological studies show that fine particulate matter (PM_2.5) is a major air pollutant associated with adverse health effects. However, nationwide observations of PM_2.5 began after 2013, which results in a lack of assessment of air pollution impact on human health before that time. Visibility is an important indicator strongly correlated with meteorological factors and air pollutants and it can be taken as an effective alternative index for atmospheric environment. Studies have shown significant correlations between visibility and health outcomes. Using long-term visibility data, we apply a semi-parametric generalized additive model to explore the association between different visibility grades and mortality risk across eight cities from 2005 to 2016. Our results indicate that the decreases in visibility level in Beijing, Shanghai, Guangzhou, Chengdu, Urumqi, and Shenyang would significantly increase the mortality risk among sensitive populations on various lag days. These findings are consistent with diagnostic results from the PM_2.5 model. The association between visibility and mortality risk indicates that visibility can serve as a proxy indicator of air quality in areas or during periods where fine particulate matter observations are unavailable. This study effectively fills the gap in health effect assessment and can provide basic information for decision-making.