Long-term impact of coal mine fire smoke on lung mechanics in exposed adults

Abstract In 2014, a six-week long fire at the Hazelwood open cut coal mine exposed residents in the adjacent town of Morwell to high concentrations of fine particulate matter with an aerodynamic diameter <2.5μm (PM 2.5 ). The long-term health consequences are being evaluated as part of the Hazelwood Health Study (HHS). Approximately 3.5 to 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 HHS. Individual fire-related PM 2.5 exposure was retrospectively modelled. Lung mechanics were assessed using the forced oscillation technique (FOT), which utilises pressure waves to measure respiratory system resistance (Rrs) and reactance (Xrs). Multivariate linear regression was used to evaluate associations between PM 2.5 and transformed Rrs5, area under the reactance curve (AX5) and Xrs5 controlling for key confounding factors. There were clear dose-response relationships between increasing mine fire PM 2.5 and worsening lung mechanics, including a reduction in post-bronchodilator Xrs5 and an increase in AX5. A 10 μg/m 3 increase in mine fire related PM 2.5 was associated with a 0.015 (95%CI: 0.004, 0.027) reduction in exponential(Xrs5) post bronchodilator, which was comparable to 4.7 years of aging. Similarly, the effect of exposure was associated with a 0.072 (0.005, 0.138) increase in natural log(AX5) post-bronchodilator, equivalent to 3.9 years of aging. This is the first study using FOT in adults evaluating long term respiratory outcomes after a medium-term ambient PM 2.5 exposure to coal mine fire smoke. These results should inform public health policies and planning for future events.