Does particulate matter modify the association between temperature and cardiorespiratory diseases?

BACKGROUND: A number of studies have shown that both temperature and air pollution are associated with health outcomes. In assessing air pollution effects, temperature is usually considered a confounder. However, only a few recent studies considered air pollution as confounders while assessing temperature effects. Few studies are available on whether or not air pollution modifies the temperature-disease relationship. METHODS: In this study, we used three parallel Poisson generalized additive models to examine whether particulate matter < 10 mu m in aerodynamic diameter (PM(10)) modified the effects of minimum temperature on cardiorespiratory morbidity and mortality in Brisbane, Australia. RESULTS: Results show that PM(10) statistically significantly modified the effects of temperature on respiratory and cardiovascular hospital admissions, all nonexternal-cause mortality, and cardiovascular mortality at different lags. The enhanced adverse temperature effects were found at higher levels of PM(10), but no clear evidence emerged for interactive effects on respiratory and cardiovascular emergency visits. Three parallel models produced similar results, which strengthened the validity of findings. CONCLUSION: We conclude that it is important to evaluate the modification role of air pollution in the assessment of temperature-related health impacts.