Heavy smoke haze that blanketed Canberra in December and January may have caused 31 deaths in the territory, a study has found.
The research, published in the Medical Journal of Australia, estimated the bushfire smoke was responsible for 417 excess deaths, 1124 hospitalisations for cardiovascular problems and 2027 for respiratory problems across ACT, NSW, Victoria and Queensland in the last quarter of 2019 and the first quarter of 2020.
In the ACT, it estimated there were 31 excess deaths, 82 cardiovascular hospital admissions, 147 respiratory admissions and 89 asthma related emergency department attendances from the smoke haze.
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 then compared deaths, cardiovascular and respiratory-related hospitalisations, and emergency department presentations with asthma to what they'd expect on any other day, according to historical data.
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That allowed them to extrapolate estimates for how many outcomes were likely caused by air pollution.
A co-author of the paper, Professor Bin Jalaludin from UNSW Medicine, said they used existing studies and health data to calculate the deaths/hospitalisations attributable to smoke pollution in the timeframe.
He said the findings were likely conservative and that the smoke-related health impact of last summer was substantial.
"Smoke is just one of many problems that will intensify with the increasing frequency and severity of major bushfires," Professor Jalaludin said.
"We urgently need to expand and diversify approaches to bushfire mitigation and adaptation to living in an increasingly hot and fire-prone country."
Excess deaths describe a temporary increase in mortality in a population, usually caused by environmental phenomena such as extreme weather events, or pandemics.
The research was led by the University of Tasmania.
Smoke haze descended on Canberra in late-November, in the same week the North Black Range and Currowan bushfires were ignited by lightning strikes.
Throughout December, air quality continued to worsen as multiple bushfires at the South Coast grew in size and ferocity.
Poor air quality peaked in Canberra on New Year's Day after the South Coast's worst fire day.
The nation's capital recorded the worst air quality index rating of the world's major cities.
Hundreds of Canberrans went to hospitals and walk-in centres for treatment during the peak of the unprecedented bushfire air-pollution crisis this summer.
There were 176 smoke-related presentations to Canberra Hospital's emergency department between December 20 and January 12, according to government figures.
