The Effects of Air Pollution on Mortality in Socially Deprived Urban Areas in Hong Kong

Abstract:

Poverty is a major determinant of population health, but little is known about its role in modifying air pollution effects. Objective In this study we examined whether people residing in socially deprived communities are at higher mortality risk from ambient air pollution. Materials and Methods We included 209 Tertiary Planning Units (TPU), the smallest units for town planning in the Special Administrative Region (SAR) of Hong Kong, China. The socioeconomic status of each TPU was measured by a social deprivation index (SDI) derived from the proportions of the population with (a) unemployment, (b) monthly household income < US$250, (c) no schooling at all, (d) one-person household, (e) never married status and (f) sub-tenancy, from the 2001 Population Census. TPUs were classified into three levels of SDI: low, middle and high. Time-series analysis with Poisson regression was performed to examine the association between changes in daily concentrations of ambient air pollution and daily number of deaths in each SDI group, for the period from January 1996 to December 2002. The differences in pollution effects between different SDI groups were evaluated using a case-only approach with logistic regression. Findings We found significant associations of NO2, SO2, PM10, and O3 with all non-accidental and cardiovascular mortality in areas of middle or high SDI (p<0.05). Health outcomes, measured as all non-accidental, cardiovascular and respiratory mortality, in people residing in high SDI areas were more strongly associated with SO2 and NO2, compared to those in middle or low SDI areas.

Conclusion: We concluded that neighborhood socioeconomic deprivation increases mortality risks associated with air pollution.