Long-term ambulance, emergency, and hospital use following mine fire-related PM _2.5 exposure: analysis of linked data

Abstract Background. The 2014 Hazelwood coal mine fire shrouded the regional Victoria, Australia town of Morwell 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. Hazelwood Health Study Adult Survey cohort data were combined with modelled air pollution data to estimate individual 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, although there were some for specific conditions including increased ambulance attendances for respiratory conditions, which attenuated over time, and injuries, which were sustained over the follow-up period. PM 2.5 exposure was associated with an increase in cardiovascular emergency presentations, but only among women, which attenuated after 2.5 years; among men, PM 2.5 exposure was associated with reductions in cardiovascular emergency presentations and hospital admissions, as well as reduced mental health hospital admissions that were sustained over the follow-up period. Conclusions. The temporary increase in respiratory ambulance attendances associated with PM 2.5 exposure aligned with previous findings on the mine fire’s effects on respiratory health. The increase in injury-related ambulance attendances is somewhat in line with prior findings and may be attributable to neurological damage from fire-related PM 2.5 exposure. Reductions in cardiovascular health service use were likely attributable to immortal time bias due to increased cardiovascular death in the first months after the fire.