Bushfire smoke: 417 deaths attributable to summer fires

MORE than 400 deaths and 3000 hospitalisations may be attributable to the bushfire smoke that shrouded Australia’s eastern states over the recent summer, researchers report in this week’s MJA.

In a preliminary evaluation of the health burden of the 2019–2020 fires, the researchers estimated that bushfire smoke was associated with 417 excess deaths, 1124 hospitalisations for cardiovascular problems, 2027 hospitalisations for respiratory problems, and 1305 emergency department presentations for asthma.

The researchers analysed hospital presentations in New South Wales, Queensland, the Australian Capital Territory and Victoria between 1 October 2019 and 10 February 2020, and defined bushfire-smoke affected days as “days on which the 24-hour mean particulate matter less than 2.5µm in diameter (PM_2.5) exceeded the 95th percentile of historical daily mean values for individual air quality stations”.

Professor Sotiris Vardoulakis, Professor of Global Environmental Health at the Australian National University’s Research School for Population Health, said the preliminary analysis provided “very useful” evidence of the substantial health impacts of bushfire smoke.

“This is a very strong public health message,” he said, noting that the 417 indirect deaths eclipsed the 34 direct deaths from the bushfires. “The impact of bushfire smoke on mortality is likely to be an order of magnitude higher than the direct impact of the fires.”

Professor Vardoulakis noted, however, that because these were “statistical deaths”, the impact was less emotive.

“It’s not people with names and addresses, so the psychological impact is different when you talk about statistical deaths.”

Associate Professor Grant Blashki, Nossal Institute for Global Health and Melbourne Sustainable Society Institute at the University of Melbourne, said the analysis was a timely resource for policy makers.

“This most welcome paper shows the value of fast turnaround analysis of data, almost in real time, so that Australian policy makers can roll out well informed adaptation measures to heatwaves and bushfires, and appreciate the urgency of strong climate mitigation policy,” he said.

Associate Professor Blashki said the findings backed up the anecdotal experience of frontline health workers in managing increased respiratory and cardiovascular disease during the high bushfire smoke exposure period.

“While the current COVID-19 pandemic is overfilling the capacity of public health, policy maker and health systems for the coming months, the paper is a reminder that mitigating climate change still needs to be high on the to-do list for Australia as one of the most vulnerable developed countries in the world to climate change.”

Professor Vardoulakis agreed.

“It is always important to highlight that the underlying causes of the Australian bushfire season were a very prolonged drought and high temperatures, which are fuelled by climate change,” he said. “Eventually, we need to address the underlying causes of the problem, which is climate change, through ambitious greenhouse gas emission mitigation strategies.”

Professor Vardoulakis said efforts to improve our understanding of the health burden of bushfire smoke were also urgently needed. And although this preliminary analysis provided an important insight into the health burdens of bushfire smoke, he said more refined research methods would enable more accurate analyses in the future.

“These findings are entirely based on the location of the air quality monitoring stations in different geographical areas and, of course, there are ways of improving exposure assessment by taking into account other characteristics like housing and socio-economic characteristics,” he said, noting that areas with older, leakier houses may have increased smoke exposure.

He said the analysis also used known exposure–response relationships, based on air pollution exposure, and further epidemiological research was needed to examine the health effects of bushfire smoke.

“The nature of urban air pollution may be different to bushfire smoke,” he said. “We don’t have conclusive evidence about that, so ideally we would need epidemiological studies looking at exposure–response relationships more specific to bushfire smoke, as well as studies into the toxicity of bushfire smoke.”

Professor Vardoulakis also renewed calls, first made in the MJA and InSight+ in February, for the establishment of an independent national expert committee on air pollution and health protection.

“We need practical advice and consistency in the way air quality data are presented and in the way the health messaging is communicated,” he said. “And, for this reason, we called for a national expert committee on air pollution and health protection.”