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Smoke from the bushfires raging near Sydney has been blanketing the city in recent weeks, reaching a crisis point on Tuesday when air pollution in parts of the city rose to more than 10 times the level deemed hazardous.
Health authorities are warning the public to be careful. Children have been forced to stay indoors during school lunchtime, ferries were cancelled and office workers were evacuated from buildings as the smoke triggered fire alarms.
These unprecedented conditions have prompted questions over what effect it could have on the population’s long-term health.
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Bushfires are so dangerous because they billow fine particulate matter, known as PM2.5, into the air. When this is breathed in, it can go deep into the lungs where it causes inflammation and enter the bloodstream to affect other parts of the body.
The link between several hours or days of poor air quality and health problems is well-established. It can worsen asthma and lung conditions such as chronic bronchitis and lead to heart attacks in people with heart disease.
People who are hospitalised or die as a result of poor air tend to have pre-existing respiratory and cardiovascular diseases. Last week, health authorities recorded a roughly 30 per cent uptick in ambulance call outs and hospitalisations, particularly in parts of the city most affected by smoke.
Less severe but longer-term exposure, such as in Beijing or New Delhi, has been linked to heart, lung and kidney disease, stroke, type 2 diabetes, sepsis and urinary tract infections. It is also associated with smaller babies, miscarriage and stillbirth.
But this isn’t necessarily true of people in Sydney, who typically enjoy relatively unpolluted air.
Fay Johnston, at the University of Tasmania, Australia, says that research on a fire in an open-cut coal mine in the country’s southeast in 2014 may shed some light on what to expect.
A nearby community was exposed to levels of smoke similar to those experience by the worst hit parts of Sydney for six weeks. In the years since, Johnston and her colleagues found that children who were exposed to the smoke while in the womb or in their first two years of life had more respiratory tract infections than those who were less exposed.
Those exposed to more smoke before the age of two had stiffer lungs than those less exposed, they found.
“But it was a subtle change,” says Johnston. “If there was a kid who was already at high risk – because they had a family history of asthma, or they also lived with smoker, or they had other risk factors – then it might be what tips the balance in getting symptoms.”
A study of infant rhesus macaque monkeys living near the 2008 California bushfires found something similar – those who were exposed to the smoke had worse lung and immune health at three years of age than those who weren’t exposed.
Neither study found much evidence that the smoke exposure had lasting effects on the respiratory health of adults, which backs up research suggesting air pollution is worse for developing children.
It may not just be physical health that’s affected. The study of around 4000 people living near the power station fire found that air pollution exposure was linked to more post-traumatic stress disorder symptoms in adults two and a half years later.
Calls to mental health lines also spike on days when the fire is the worst, the Sydney Morning Herald reports.
Linda Selvey, of the Royal Australasian College of Physicians, says that research on quitting cigarette smoking may be reassuring to those worried about short-term exposure to poor air. “For lung cancer, the risk is never completely eliminated – but gradually the risks [of other health conditions] return to similar levels to people who never smoked,” she says.
The World Health Organization recently found that improving air quality can have dramatic and quick health benefits.
Nevertheless, the air quality may continue to be poor in the coming weeks or even months, with the Bureau of Meteorology predicting a longer and hotter summer than normal and fire experts fearing the worst is yet to come.
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