Aims and objectives
Ambient PM2.5 is associated with higher rates of COVID-19 infection and severe disease. Yet it is unclear whether medium-term extreme PM2.5 events such as coalmine fires also increase risk, or how long the vulnerability lasts. We evaluated COVID-19 outcomes in a cohort of people exposed to smoke from the 2014 Hazelwood coalmine fire.
Methods
In late 2022, we surveyed members of an Adult Cohort to determine long-term health effects of the coalmine fire. COVID-19 infections were identified with validated self-report tools and symptom-based algorithms. PM2.5exposure was determined from time location diaries and modelled air pollution estimates. Hospitalisation for COVID-19 served as a proxy for severity. We conducted logistic regressions, and adjusted for demographics, smoking, socioeconomic status and asthma/COPD.
Results
Of 612 participants completing the survey, 44% (n=271) either reported or met the symptom threshold for a COVID-19 infection. A 1SD increase in PM2.5 exposure was associated with 14% higher odds of infection (OR=1.14, 95%CI: 0.88-1.47, p=0.312). Results were similar in crude models (OR=1.08; 95%CI: 0.92-1.27). There were too few hospitalisations (n=7, 1%) to conduct severity analyses.
Conclusions
PM2.5 from a coalmine fire was not significantly associated with COVID-19 infections 6-8 years later, though direction of association was consistent with evidence indicating that PM2.5 increases risk. As climate change will increase the frequency of fire events and the COVID-19 pandemic shows no signs of abating, it would be prudent to treat the association as real until additional evidence becomes available.