By Angus Dalton
A likely El Niño weather event is expected to worsen Sydney’s air pollution, as a raft of studies build further evidence that fine atmospheric particles are linked to higher incidences of lung cancer, dementia, depression and ADHD.
The recent research includes a data analysis of 164,000 Chinese schoolchildren that found for every 10 micrograms of PM2.5 (particles smaller than 2.5 microns) per cubic metre they were exposed to, children were 1.65 times more likely to be diagnosed with ADHD.
Sydney air pollution spikes during bushfires but even normal levels can be dangerous, experts warn.Credit: Kate Geraghty
The average PM2.5 in one of the cities, Kashgar, was almost 115 micrograms per cubic metre, far higher than Sydney’s average annual air standard of 8 micrograms. But there are no safe levels of air pollution, warned co-author of the study Professor Yuming Guo.
“We hope this informs policymakers and the general population to take action to reduce the impact of air pollution,” Guo, a global authority on air pollution and health at Monash University, said. “This is the largest study [about ADHD and air pollution] and the evidence is very robust.”
Other recent studies found higher levels of air pollution are associated with higher odds of depression in people older than 64, irregular heartbeat, dementia and lung cancer. The tiny PM2.5 particles, a fraction of the width of a human hair, are thought to affect health because they travel deep into the lungs and bloodstream.
Wetter, cooler years see better air quality while fine particle levels are likely to increase if an El Niño forms and brings drought and bushfires to NSW, wrote the authors of the Atmosphere paper A Clean Air Plan for Sydney.
Exposure to pollutants is higher for people who live near roads – particularly intersections, where vehicles stop and start – and in urban corridors bordered by high buildings that trap pollution, referred to as “street canyons” by Dr Hugh Forehead at the University of Wollongong.
A few years ago, Forehead, an expert in air quality data, and other researchers at the university rigged up a pram with a pollutant monitor and sent students trundling along Anzac Parade in Randwick.
The pollutant levels picked up by the makeshift pram monitor were far higher than indicated by the government’s background monitoring system. The discovery prompted Forehead to conduct a study in Liverpool that found street-level pollution was up to 10 times worse than reported by government air monitors.
South-west Sydney has the worst levels of pollution and the most days when levels of PM2.5 surpass the NSW government maximum target of 25 micrograms per cubic metre. During 2019, a bad year for air pollution due to Black Summer fires, Liverpool had 32 days when PM2.5 surpassed targets compared to Randwick’s 18.
“It’s an unfortunate fact of the geography,” Forehead said. “When the sea breeze comes in, the hills are up behind south-western Sydney and all the pollution sort of piles up. It blows off the city and just ends up in that part of the Sydney basin.”
The major sources of air pollution are wood heaters, industry, motor vehicles and power stations.
A long-term government study released in February found air pollution in NSW increased health costs by $5.8 billion and caused more than 600 premature deaths each year.
The average annual level of PM2.5 in Sydney was 6.43 micrograms per cubic metre, higher than the recommendation set by the World Health Organisation of 5 micrograms. But that’s far better than the worldwide average, estimated by Guo to be 32.8 micrograms per cubic metre between 2000 and 2019.
“Australia has a very low level of concentration [of pollutants],” Guo said. “This does not mean Australia is safe because at that low level of air pollution, there is still risk.”
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