Health impacts of the 2019–2020 Australian “Black Summer” bushfires: smoke-related asthma emergency department presentations in New South Wales and the Australian Capital Territory

Bushfires contribute to environmental pollution in the form of Particulate Matter (PM). PM with an aerodynamic diameter of ≤ 2.5 μm (PM_2.5) is relevant to individuals with chronic respiratory diseases such as asthma. These particles tend to enter the bloodstream and activate inflammatory processes, leading to asthma exacerbation. This study examines this environmental-health relationship in the context of the 2019-2020 "Black Summer" bushfires in New South Wales (NSW) and the Australian Capital Territory (ACT) regions of Australia. Weekly measurements of emergency department (ED) presentations for asthma from 1 September 2019 to 29 February 2020 were collected and compared to weekly averages of PM_2.5, meteorological data, and other relevant covariables. To control for seasonal changes in ED presentations unrelated to bushfire smoke, the observed PM_2.5 values and ED presentations were subtracted from corresponding values the year prior. A quasi-Poisson generalised linear model (GLM) was used to assess the impact of PM_2.5 and these covariables on weekly ED presentations for asthma. The model explained approximately 33% of the variance in asthma presentations with PM_2.5, minimum temperature and relative humidity being the most significant covariables. These findings provide insight into this environmental-health relationship and support public health planning for smoke-related asthma presentations.