Mortality burden attributable to exceptional PM 2.5 air pollution events in Australian cities: A health impact assessment.

BACKGROUND: People living in Australian cities face increased mortality risks from exposure to extreme air pollution events due to bushfires and dust storms. However, the burden of mortality attributable to exceptional PM 2.5 levels has not been well characterised. We assessed the burden of mortality due to PM 2.5 pollution events in Australian capital cities between 2001 and 2020.

METHODS: For this health impact assessment, we obtained data on daily counts of deaths for all non-accidental causes and ages from the Australian National Vital Statistics Register. Daily concentrations of PM 2.5 were estimated at a 5 km grid cell, using a Random Forest statistical model of data from air pollution monitoring sites combined with a range of satellite and land use-related data. We calculated the exceptional PM 2.5 levels for each extreme pollution exposure day using the deviation from a seasonal and trend loess decomposition model. The burden of mortality was examined using a relative risk concentration-response function suggested in the literature.

FINDINGS: Over the 20-year study period, we estimated 1454 (95 % CI 987, 1920) deaths in the major Australian cities attributable to exceptional PM 2.5 exposure levels. The mortality burden due to PM 2.5 exposure on extreme pollution days was considerable. Variations were observed across Australia. Despite relatively low daily PM 2.5 levels compared to global averages, all Australian cities have extreme pollution exposure days, with PM 2.5 concentrations exceeding the World Health Organisation Air Quality Guideline standard for 24-h exposure. Our analysis results indicate that nearly one-third of deaths from extreme air pollution exposure can be prevented with a 5 % reduction in PM 2.5 levels on days with exceptional pollution.

INTERPRETATION: Exposure to exceptional PM 2.5 events was associated with an increased mortality burden in Australia's cities. Policies and coordinated action are needed to manage the health risks of extreme air pollution events due to bushfires and dust storms under climate change.