Extreme air pollution events from bushfires and dust storms and their association with mortality in Sydney, Australia 1994–2007

IntroductionExtreme air pollution events due to bushfire smoke and dust storms are expected to increase as a consequence of climate change, yet little has been published about their population health impacts. We examined the association between air pollution events and mortality in Sydney from 1997 to 2004.MethodsEvents were defined as days for which the 24 h city-wide concentration of PM10 exceeded the 99th percentile. All events were researched and categorised as being caused by either smoke or dust. We used a time-stratified case-crossover design with conditional logistic regression modelling adjusted for influenza epidemics, same day and lagged temperature and humidity. Reported odds ratios (OR) and 95% confidence intervals are for mortality on event days compared with non-event days. The contribution of elevated average temperatures to mortality during smoke events was explored.ResultsThere were 52 event days, 48 attributable to bushfire smoke, six to dust and two affected by both. Smoke events were associated with a 5% increase in non-accidental mortality at a lag of 1 day OR (95% confidence interval (CI)) 1.05 (95%CI: 1.00–1.10). When same day temperature was removed from the model, additional same day associations were observed with non-accidental mortality OR 1.05 (95%CI: 1.00–1.09), and with cardiovascular mortality OR (95%CI) 1.10 (95%CI: 1.00–1.20). Dust events were associated with a 15% increase in non-accidental mortality at a lag of 3 days, OR (95%CI) 1.16 (95%CI: 1.03–1.30).ConclusionsThe magnitude and temporal patterns of association with mortality were different for smoke and dust events. Public health advisories during bushfire smoke pollution episodes should include advice about hot weather in addition to air pollution.

► We assessed the mortality impacts of bushfire smoke and dust storms in Sydney, Australia.
► Smoke and dust pollution events were both associated with increased mortality.
► Increased temperature contributed to excess mortality during bushfire smoke events.