Background In 2014, the Hazelwood coalmine fire in regional Victoria, Australia shrouded nearby communities in smoke for six weeks. Prior investigations identified substantial adverse effects, including increases in the use of health services. In this study, we examined the effects on hospital and ambulance use in the eight years following the fire. Methods Using Victorian hospital (Jan 2009-Jun 2022) and ambulance (Jan 2013-Dec 2021) data, we conducted an interrupted time series of changes to the rate of hospital admissions, emergency presentations, and ambulance attendances. A categorical exposure model compared two locations, most-exposed Morwell and less-exposed Latrobe Valley, to the rest of regional Victoria. A continuous exposure model used spatial estimates of fire-related PM2.5. Analyses were stratified by sex, age group (<65/65+ years), and condition (cardiovascular, respiratory, mental health, injury). Results There were small but significant increases in overall hospital admissions and emergency presentations across all analyses, but little evidence of change in overall ambulance attendances. Effects varied considerably by condition, with the biggest relative increases observed among hospital admissions for mental health conditions and injuries. While cardiovascular-related hospital admissions and emergency presentations increased post-fire, ambulance attendances decreased. Conclusions Our findings suggest the Hazelwood coalmine fire likely increased hospital usage. However, it is unclear whether this was due to the direct effects of smoke exposure on health, or the disruptive socioeconomic and behavioural impacts of an environmental disaster that affected how communities engaged with various health services.

MJA holds investigator-initiated grants for unrelated research from Pfizer, Boehringer-Ingelheim, Sanofi and GSK. He has undertaken an unrelated consultancy for and received assistance for conference attendance from Sanofi. He also received a speaker's fee from GSK. YG was supported by a Career Development Fellowship of the Australian National Health and Medical Research Council (APP1163693). RX is supported by VicHealth Postdoctoral Research Fellowships 2022. EH is supported by an NHMRC post-graduate scholarship. All other authors declare they have nothing to disclose.

This work was funded by the Victorian Department of Health. The paper presents the views of the authorsand does not representthe views of the Department.

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THE Monash University Human Research Ethics Committee (MUHREC) of Monash University gave ethical approval for this work as part of the Hazelwood Adult Survey & Health Record Linkage (approval number: 25680).

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