All-cause and cardiac mortality in relation to smoke exposure nine 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 paper evaluates smoke effects on mortality 9-years after the fire. MethodsIn 2016-17, 4,056 members of the exposed community and a demographically-similar control were recruited into a cohort study. A third of these (2,725 (67%)) consented to linkage of their data. To estimate individual-level smoke exposure, participants time-location diaries were blended with estimates of hourly fire-related PM2.5 based on meteorological and chemical transport models. All-cause mortality data were obtained up to mid-2023 by linkage with the National Death Index. Cardiac-related deaths were identifiable up to December 2021 and predicted thereafter to mid-2023. Differences in all-cause mortality were evaluated with Cox proportional-hazards models and differences in cardiac mortality with a competing risk survival model. ResultsAcross 6-7 years of follow-up, 303 (11%) of the sample died. All-cause mortality was not associated with PM2.5 exposure. A 10{micro}g/m3 increase in PM2.5 was associated with a 17% (95%CI: 1.01-1.36) higher risk of mortality from cardiac causes. DiscussionPM2.5 from the mine fire was associated with elevated cardiac mortality between 2-9 years post-exposure. This finding concords with a growing body of evidence after acute exposure to wildfires and chronic exposures from household or ambient air pollution. Measures are needed to protect individuals from exposure to smoke during and after large fire events.