Daily Visibility and Mortality: Assessment of Health Benefits From Improving Visibility in Hong Kong

Abstract

PP-31-017 Background/Aims: Visibility in Hong Kong has deteriorated significantly over 40 years with the frequency of visibility below 8 km in the absence of fog, mist, or precipitation, increasing from 6.6 days in 1968 to 54.1 days in 2007. Methods: During 1996–2006, we obtained mortality data for all natural and cardiorespiratory causes, visibility recorded as visual range in kilometers, temperature and relative humidity from an urban observatory, and concentrations of 4 criteria pollutants. A generalized additive Poisson regression model with penalized cubic regression splines was fitted to control for time–varying covariates. Results: For all natural causes of mortality an interquartile range of 6.5 km increase in visibility at lag 0–1 days was associated with an excess risk (ER%) (95% Confidence Interval) of −1.13 [−1.76, −0.49] for all ages and −1.37 [−2.09, −0.65] for ages 65+; for cardiovascular mortality of −1.31 [−2.49, −0.13] for all ages, and −1.72 [−3.00, −0.44] for ages 65+; for respiratory mortality of −1.92 [−3.35, −0.49] for all ages and −1.76 [−3.25, −0.28] for ages 65+. The estimated ER% for daily mortality derived from both visibility and air pollutant data were comparable in terms of magnitude, lag pattern, and dose-response relationships especially when using particulate matter with aerodynamic diameter ≤10 μm to predict mortality associated with visibility. Conclusion: Visibility provides a useful proxy for the assessment of environmental health risks from ambient air pollutants and a valid approach for the assessment of the public health impacts of air pollution and the benefits of air quality improvement measures in developing countries where pollutant monitoring data are scarce.