Australia Air pollution resulting from controlled burning near Sydney was so severe it probably caused 14 premature deaths in May and sent dozens of people to hospital, according to a new health study.
The research, published in The Medical Journal of Australia, used statistical models to identify baseline deaths and cardiovascular and respiratory hospitalisation rates. It found about a 5 per cent increase during a six-day period last autumn of high pollution over the city.
“It was one of the worst events in Sydney’s history”, comparable with the pollution from major bushfires, said Fay Johnston, head of the Environment and Health research group at the University of Tasmania. “Conditions were perfect for hazard-reduction burns, and there were many burns.”
The most dangerous form of pollution involves particles of 2.5 microns or smaller. Such particulates – roughly one-sixth the width of a human hair – can enter the lungs or bloodstream and damage the health of the young, the old or those with chronic conditions.
During the worst days of the smoke haze, some parts of Sydney were averaging more than six times the level considered safe, sending an additional 101 people to hospital. (See chart below.)
With the ideal conditions, many small fires were lit by the Rural Fire Service around Sydney with much of the smoke settling in the basin. “They’ve got targets to reach and they carried on burning despite that [smoke], and that’s when it really built up,” Dr Johnston said.
The “extreme episode” should prompt authorities to give greater scope for smoke in their modelling and encourage better warning approaches to minimise the risk for vulnerable members of the community, she said.
Rob Rogers, deputy RFS commissioner, said hazard reduction burns were “an important tool in reducing the impact of serious bush fires which can have devastating effects on entire communities”, and the agency was working with other authorities to try to reduce the smoke risks.
“There is a delicate balance between ensuring this important work is completed, and limiting the effects of smoke,” Mr Rogers said, adding the best conditions for such fires often result in the formation of low level inversion patterns at night which trap in smoke longer than current predictive modelling suggests.
“Where it’s identified that there may be a health or community impact from smoke, we consider ways of minimising those risks,” he said. “This includes changes to the times that hazard reductions are conducted, lighting patterns, or rescheduling burns.”
Officials have said authorities made the most of the relatively calm conditions earlier this year, burning almost 200,000 hectares across the state in autumn.
That burning has been helpful in curbing fire risks given that the wetter-than-usual winter for much of NSW limited controlled fires during the spring.
A Health Department spokesperson said the research was consistent with “well-established methods used in health impact assessment”.
Hazard reduction burning had important benefits “for health and society more broadly, such as protection of property”, the spokesperson said. Still, the study was “an important starting point in assessing how the health impacts can be minimised”.
Dr Johnston spoke to Fairfax Media from Los Angeles where she will attend an international smoke symposium. She supports controlled burns but noted the need to incorporate smoke management more closely in fire plans.
In Tasmania, for instance, fire managers covering 17 regions of the state have to bid for controlled burning quotas to ensure pollution risks are reduced. The results had been “dramatic…and barely held up burning”.
Improved communication with the public was also important to ensure those with existing conditions, such as asthma, could take preventative measures. Others could try to seal their homes as much as possible in advance.
Authorities in different states, including NSW, were already working to improve modelling to identify where smoke will move and when it was likely to clear.
“Burning is the best tool we have but it has its limitations,” Dr Johnston said, adding that for some communities living near the bush, efforts to remove vegetation without fires could bring similar risk-reduction benefits with needing fires.
“We’re experiencing more fires, we’re experiencing more fire weather,” she said. “We can get a lot better at it than where we are now.”
Climate change is likely to make things worse in the future.
“With global warming, we think the fire season will be longer, and bushfires more intense and lasting longer,” said Geoffrey Morgan from the University of Sydney and another author of the paper. That may shorten the time available for reduction burning even more.
Bin Jalaludin, from the Ingham Institute for Applied Medical Research at Liverpool Hospital, said the public often accepted bushfire smoke as a typical hazard of life in Australia.
“But if there was a factory that poured out smoke for six days, we’d be up in arms,” Professor Jalaludin said. “And the effects may be exactly the same”.
He said the research into Sydney’s deaths was relatively new for Australia but noted that studies of the huge fires in Indonesia last year caused as many as 100,000 premature deaths across south-east Asia.
The Baird government, meanwhile, has a discussion paper on air pollution management options out for public comment until next January, with the reduction of emissions from hazard reduction burning within its scope.