Mortality in relation to smoke exposure 9 years after the Hazelwood coal mine fire.

backgroundIn 2014, a coal mine fire in rural Australia shrouded nearby towns in smoke for several weeks. In response to community concerns and a lack of available evidence, the Victorian Department of Health commissioned a long-term health study. This article evaluates smoke effects on mortality 9 years after the fire.

methodsIn 2016-17, 2872 individuals living near the mine during the fire were recruited into a cohort study and consented to linkage of their data. Time-location diaries were blended with estimates of hourly fire-related fine particulate matter ≤2.5 µm (PM2.5) to generate individual exposure measures. Mortality data were obtained up to mid-2023 by linkage with the National Death Index. Cardiac, cancer, and respiratory-related deaths were identifiable up to December 2021 and predicted thereafter to mid-2023. All-cause mortality effects were evaluated with Cox proportional-hazards models and cause-specific mortality with a competing risk survival model.

resultsNine years post-fire, 318 (11%) of the sample had died. All-cause mortality was not associated with PM2.5 exposure. There was no detectable effect on cancer deaths. However, a 10 µg/m3 increase in daily mean exposure to fire-related PM2.5 was associated with an 18% (95% CI: 2%-37%) higher risk of cardiac mortality, while PM2.5 exacerbated risk of respiratory mortality from tobacco use.

conclusionFire-related PM2.5 increased cardiac mortality and smoking effects on respiratory mortality years after the event. These findings concord with a growing body of evidence on the deadly risks of wildfire smoke. Protecting communities and individuals from smoke during and after large fire events should be a public health priority.