Smoke from the disastrous 2019-20 bushfire season caused more than 400 excess deaths, new research has found
Researchers led by Nicolas Borchers Arriagada, a PhD candidate with the Menzies Institute for Medical Research at the University of Tasmania, investigated the health burden attributable to air pollution generated by bushfires between 1 October 2019 and 10 February 2020.
The research was published in the Medical Journal of Australia.
Data were obtained from the NSW Department of Planning, Industry and Environment, the Queensland Department of Science, ACT Health, and the Environmental Protection Agency Victoria.
The researchers defined bushfire smoke-affected days as days on which the 24-hour mean PM2.5 concentration exceeded the 95th percentile of historical daily mean values for individual air quality stations.
They also used data from the Australian Bureau of Statistics, the Australian Institute of Health and Welfare, and the NSW Ministry of Health.
“During the study period, PM2.5 concentrations exceeding the 95th percentile of historical daily mean values were recorded by at least one monitoring station in the study area on 125 of 133 days,” the authors wrote.
“The highest population-weighted PM2.5 exposure level, 98.5 μg/m3 on 14 January 2020, exceeded the national air quality 24-hour standard (25 μg/m3) and was more than 14 times the historical population-weighted mean 24-hour PM2.5 value of 6.8 μg/m3.
“We estimated that bushfire smoke was responsible for 417 (95% CI, 153–680) excess deaths, 1124 (95% CI, 211–2047) hospitalisations for cardiovascular problems and 2027 (95% CI, 0–4252) for respiratory problems, and 1305 (95% CI, 705–1908) presentations to emergency departments with asthma.
“Applying lower thresholds for defining bushfire smoke-affected days (no threshold, 90th percentile of historical values) did not markedly alter our findings; a higher threshold (99th percentile) reduced the estimates by about 20%.
“The highest population-weighted PM2.5 exposure level, 98.5 μg/m3 on 14 January 2020(Box 1), exceeded the national air quality 24-hour standard (25 μg/m3)19 and was more than fourteen times the historical population-weighted mean 24-hour PM2.5 value of 6.8 μg/m3.”
The researchers note that they did not included data for smoke from all extreme fires in Australia during the study period, instead only looking at air quality data from monitoring stations in the four eastern states.
They also did not attempt to estimate health effects for which exposure-response relationships were less well characterised – including primary health care attendances and ambulance calls.
“Our findings indicate that the smoke-related health impact was substantial,” the authors concluded.
“Smoke is just one of many problems that will intensify with the increasing frequency and severity of major bushfires associated with climate change.
“Expanded and diversified approaches to bushfire mitigation and adaptation to living in an increasingly hot and fire-prone country are urgently needed.”