In February 2014, the coalmine adjacent to the Hazelwood Power Station in the Latrobe Valley of Victoria, Australia, caught fire, with residents from the nearby town of Morwell and the wider area exposed to smoke for six weeks. Although there was evidence linking the mine-fire event with psychological distress, no studies have evaluated the degree of distress in relation to the level of smoke exposure. We aimed to investigate the exposure-response relationship between particulate matter 2.5μm or less in diameter (PM2.5) released during the Hazelwood mine fire event and long-term symptoms of posttraumatic distress in the affected community, including the consideration of other key factors. A total of 3,096 Morwell residents, and 960 residents from the largely unexposed comparison community of Sale, were assessed for symptoms of posttraumatic distress 2.5 years after the Hazelwood incident using the Impact of Events Scale-Revised (IES-R). Individual-level PM2.5 exposure was estimated by mapping participants' self-reported location data on modelled PM2.5 concentrations related to the mine fire. Multivariate linear regression was used to evaluate the exposure-response relationship. Both mean and peak exposure to mine fire-related PM2.5 were found to be associated with participant IES-R scores with an interaction effect between age and mean PM2.5 exposure also identified. Each 10 µg/m 3 increase in mean PM2.5 exposure corresponded to a 0.98 increase in IES-R score (95% CI: 0.36 to 1.61), and each 100 µg/m 3 increase in peak PM2.5 exposure corresponded to a 0.36 increase (95% CI: 0.06 to 0.67). An age-effect was observed, with the exposureresponse association found to be stronger for younger adults. The results suggest that increased exposure to PM2.5 emissions from the Hazelwood mine fire event was associated with higher levels of psychological distress associated with the mine fire and the most pronounced effect was on younger adults living in the affected community. Main findings: There is an exposure-response relationship between Pm2.5 released from the Hazelwood mine fire event and long-term psychological distress towards the event. The exposure-response relationship is more pronounced in younger adults than older adults.

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Introduction. In 2014 the Hazelwood open cut coal mine burned for six weeks, exposing nearby residents to fine particulate matter (PM2.5). The long-term health consequences are being evaluated as part of the Hazelwood Health Study (HHS). These analyses explore the association between PM 2.5 and chronic obstructive pulmonary disease (COPD).Methods. A sample of 346 exposed, and 173 unexposed, adults participated in the longitudinal Respiratory Stream of the HHS. Participants underwent spirometry and gas transfer measurements and answered validated respiratory questionnaires 3.5-4 years after the fire. Individual level mine fire-related PM2.5 exposure was modelled. Multivariate linear regression and logistic models were fitted to analyse associations between mean and peak PM2.5 exposure and clinical outcomes, stratified by smoking status.Results. A 10 μg/m 3 increase in mean PM2.5 exposure was associated with a 69% (95%CI: 11% to 158%) increase in odds of spirometry consistent with COPD amongst non-smokers and increased odds of chest tightness (odds ratio; OR 1.30, 95%CI 1.03 to 1.64) and chronic cough (OR 1.24, 95%CI 1.02 to 1.51) in the previous 12 months in all participants. For current smokers, increments in mean PM2.5 exposure were associated with higher odds of chronic cough in the preceding 12 months (OR 2.13, 95%CI 1.24 to 3.65).Discussion. Almost four years after a six-week period of coal fire PM2.5 exposure, we identified a doseresponse association between exposure and COPD in non-smokers. With climate change a likely contributor to increased risk of landscape fires, the findings will inform policy decisions during future sustained smoke events. KEY MESSAGESWhat is the key question? Are there long-term impacts of a six-week mine fire event generating PM2.5 on COPD and related respiratory symptoms in adults?What is the bottom line? Almost 4 years after the mine fire, each 10 µg/m 3 increase in PM2.5 exposure was associated with a 69% increase in odds of spirometry consistent with COPD amongst non-smokers, and a 30% increase in odds of chest tightness and 24% increase in odds of chronic cough amongst all participants. Amongst smokers, each 10 µg/m 3 increase in PM 2.5 was associated with a 113% increase in odds of chronic cough. Why read on?With the recent megafires in Australia and the United States exposing communities to smoke for weeks to months, evidence of the long-term health impacts of similar duration PM2.5 generating pollution events are needed to inform the public health response.

Background and objective In 2014, a 6‐week‐long fire at the Hazelwood coal mine exposed residents in the adjacent town of Morwell to high concentrations of fine particulate matter with an aerodynamic diameter < 2.5 μm (PM2.5). The long‐term health consequences are being evaluated as part of the Hazelwood Health Study. Methods Approximately 3.5–4 years after the mine fire, adults from Morwell (n = 346) and the comparison town Sale (n = 173) participated in the longitudinal Respiratory Stream of the Study. Individual PM2.5 exposure was retrospectively modelled. Lung mechanics were assessed using the forced oscillation technique (FOT), utilizing pressure waves to measure respiratory system resistance (Rrs) and reactance (Xrs). Multivariate linear regression was used to evaluate associations between PM2.5 and transformed Rrs at 5 Hz, area under the reactance curve (AX5) and Xrs at 5 Hz controlling for key confounders. Results There were clear dose–response relationships between increasing mine fire PM2.5 and worsening lung mechanics, including a reduction in post‐bronchodilator (BD) Xrs5 and an increase in AX5. A 10 μg/m3 increase in mine fire‐related PM2.5 was associated with a 0.015 (95% CI: 0.004, 0.027) reduction in exponential (Xrs5) post‐BD, which was comparable to 4.7 years of ageing. Similarly, the effect of exposure was associated with a 0.072 (0.005, 0.138) increase in natural log (lnAX5) post‐BD, equivalent to 3.9 years of ageing. Conclusion This is the first study using FOT in adults evaluating long‐term respiratory outcomes after medium‐term ambient PM2.5 exposure to coal mine fire smoke. These results should inform public health policies and planning for future events.

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