Changes in daily air pollution and mortality in Perth : a case crossover study

The monitoring of the common air pollutants in Perth has shown that concentrations exceed national standards for particles and photochemical oxidants (measured as ozone [O3]) on occasions in winter and summer respectively. By contrast, concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2) and carbon monoxide (CO) are all below national standards. In this study, a time stratified case crossover design was used to investigate the relationship between changes in daily air pollutant concentrations and mortality in Perth. The data were analysed using conditional logistic regression to produce odds ratios. Mortality data were categorised into cardiovascular disease, respiratory disease, and 'other mortality' and were obtained for the period 1992 through 1998. Network air quality data and meteorological data were obtained for the same period. The results showed significant relationships between cardiovascular mortality and NO2 and O3 concentrations. Increased odds ratios were also observed for O3 concentrations and respiratory mortality, however, only for the 8-hour O3 concentration was the increase statistically significant. A significant odds ratio was also observed for changes in CO concentrations and 'other mortality'. The data support the findings of other Australian and international studies and will assist in the evaluation of strategies designed to reduce air pollution in Perth.