Smoke blanketed large parts of eastern Australia late last year.Credit: Brent Lewin/Bloomberg/Getty

Researchers estimate that smoke pollution probably killed more than 400 people during the unprecedented bush fires across southeast Australia from November to February. Thirty-three people were killed in incidents directly related to the fires.

Air-pollution researcher Fay Johnston at the University of Tasmania in Hobart led a team that collected data on the average number of emergency-department admissions, hospitalizations and deaths on any given day throughout the year. The researchers mapped detailed data on air-pollution levels from 1 October to 10 February and modelled how these would have increased the emergency admissions.

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They found that there could have been around 417 additional deaths and 1,305 emergency-department admissions for asthma attacks over the period of the fires. An extra 3,151 people could also have been admitted to hospital for heart and respiratory problems.

The results are reported in the 23 March edition of The Medical Journal of Australia, and are the first published estimate of the scale of the medical impact of the bush-fire smoke1. Johnston estimates that the haze affected around 80% of Australia’s 25 million people, in some cases for many weeks at a time.

“In terms of the extent and duration of the fires, and pollution in the air, this is off the chart for a single summer fire season,” she says.

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Research such as this, which estimates the true impact of smoke pollution on the population, is important, says Guy Marks, an epidemiologist who studies respiratory diseases at the University of New South Wales in Sydney, Australia.

“These deaths and hospitalizations would not have been recognized as being attributable to the fires and smoke at the time they occurred. Hence, they tend to have less attention paid to them,” adds Marks.