Daily visibility and mortality: Assessment of health benefits from improved visibility in Hong Kong

Thuan Quoc Thach, Chit Ming Wong, King Pan Chan, Yuen Kwan Chau, Yat Nork Chung, Chun Quan Ou, Lin Yang, Anthony J. Hedley

Research output: Journal article publicationJournal articleAcademic researchpeer-review

51 Citations (Scopus)


Visibility in Hong Kong has deteriorated significantly over 40 years with 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. We assessed the short-term mortality effects of daily loss of visibility. During 1996-2006, we obtained mortality data for non-accidental and cardiorespiratory causes, visibility recorded as visual range in kilometers, temperature, and relative humidity from an urban observatory, and concentrations of four criteria pollutants. A generalized additive Poisson regression model with penalized cubic regression splines was fitted to control for time variant covariates. For non-accidental mortality, an interquartile range (IQR) of 6.5. km decrease in visibility at lag. 0-1 days was associated with an excess risk (ER%) [95% CI] of 1.13 [0.49, 1.76] for all ages and 1.37 [0.65, 2.09] for ages 65 years and over; for cardiovascular mortality of 1.31 [0.13, 2.49] for all ages, and 1.72 [0.44, 3.00] for ages 65 years and over; and for respiratory mortality of 1.92 [0.49, 3.35] for all ages and 1.76 [0.28, 3.25] for ages 65 years and over. The estimated ER% for daily mortality derived from both visibility and air pollutant data were comparable in terms of magnitude, lag pattern, and exposure-response relationships especially when using particulate matter with aerodynamic diameter ≤10γm to predict the mortality associated with visibility. 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.
Original languageEnglish
Pages (from-to)617-623
Number of pages7
JournalEnvironmental Research
Issue number6
Publication statusPublished - 1 Aug 2010
Externally publishedYes


  • Air pollution
  • Hong Kong
  • Mortality
  • Time series
  • Visibility

ASJC Scopus subject areas

  • Biochemistry
  • General Environmental Science


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