Spatial patterns of mortality in relation to particulate air pollution in Christchurch, 1988-1997

This paper describes an analysis of mortality among census areas in the city of Christchurch, New Zealand. The number of deaths following days with high particulate air pollution were compared with deaths on matched unpolluted days. The possible role of population age structure, relative deprivation (estimated using the NZDep96 index) and local exposure to outdoor air pollution from household fires (estimated using a chimney density index) was explored. There was a statistically significant association between mortality and air pollution. We found substantial variation in pollution-related mortality among census area units. Relative deprivation (but not the proportion of elderly people or chimney density) was found to be a statistically significant predictor of mortality patterns. There was also a positive association between chimney density and relative deprivation. These findings suggest that relative deprivation may increase vulnerability to the effects of particulate air pollution on daily mortality, independently of the effects of age and local variation in exposure.