Ambulance and hospital use after a coal mine fire: Analysis of linked data

Background The 2014 Hazelwood coal mine fire shrouded the town of Morwell in regional Victoria, Australia, in smoke for six weeks. Building on previous analyses, we explored linked survey and healthcare data to investigate longer-term effects of fire-related PM ^2.5 exposure on ambulance attendances, emergency department presentations, and hospital admissions. Methods The Hazelwood Health Study Adult Survey cohort data were combined with modelled air pollution data to estimate individual levels of fire-related PM ^2.5 exposure and linked with ambulance, emergency department, and hospital admission data up to 2022. Associations between fire-related PM ^2.5 and health service use were evaluated using a recurrent event survival model over the 8-year post-fire period and within time strata (<2.5 years, 2.5-5 years, >5 years) and by condition, sex, and age. Results There were no detectable effects of fire-related PM ^2.5 on overall health service use in the total 8-year post-fire period, although there were some for specific conditions. PM ^2.5 exposure was associated with increased ambulance attendances for respiratory conditions, which attenuated over time, and injuries, which were sustained over the follow-up period. PM ^2.5 was also associated with temporary increase in cardiovascular emergency presentations and reduced cardiovascular hospital admissions. The reductions in cardiovascular emergency presentations and hospital admissions were only detectable among men. Conclusions The short-lived effect of PM ^2.5 on respiratory hospital admissions aligned with previous findings on the mine fire's effects on respiratory health. The increase in injury-related ambulance attendances also aligns with prior findings and might be attributable to neurological damage from fire-related PM ^2.5 exposure. Reductions in cardiovascular health service use were new and likely attributable to immortal time bias due to previously-identified rises in cardiovascular death in the first months after the fire.