Whether from backburning or bushfires, hazy smoke lingering over homes across the country is a regular part of summer in Australia.
But the clouds can be more serious than just an unpleasant smell – smoke can be a significant health hazard for many people.
This is what you need to know about the health risks, and what you can do to mitigate them.
How harmful is bushfire smoke?
Known as PM2.5, these particles have a diameter of 2.5 micrometres or less – that is, 2.5 millionths of a metre – and can be easily breathed in as they circulate through the air.
That can, in turn, exacerbate existing health conditions like asthma, and can contribute to heart disease and decreased life expectancy, even in small exposure levels.
"As a bushfire burns, a mixture of fine particles and toxic gases are released into the air as smoke, and these particles can go deep into the lungs, enter the blood and travel throughout the body," Lung Foundation Australia acting CEO Christa Bayer said.
"Short-term, breathing in these particles can exacerbate existing health issues, impair lung function, and increase hospitalisation and death rates. There is no safe level of air pollution.
"Exposure to these particles can cause lung cancer, as well as a range of other conditions including pneumonia, chronic obstructive pulmonary disease (COPD), heart disease, stroke, worsen asthma and other respiratory conditions, and has even been linked to diabetes, adverse pregnancy outcomes and neurological diseases."
Is bushfire smoke carcinogenic?
Bushfire smoke is classified by the International Agency for Research on Cancer as a possible (Class 2B) carcinogen for firefighters who are exposed to it as part of their occupation.
The Australian Health Department notes there is a "casual association" between bushfire smoke and lung cancer, but says there's no hard evidence linking the two – although the Lung Foundation Australia says smoke can cause cancer.
Striking photos that captured horrors of the Black Summer bushfires
Who is most at risk from bushfire smoke?
People who have existing respiratory conditions, such as asthma, can be particularly vulnerable to bushfire smoke, but the Health Department says other groups are also at risk.
"As there is limited information about the long-term implications of prolonged exposures, research is ongoing to better characterise these longer-term health effects, particularly across groups at higher risk, such as those with chronic conditions, very young children, pregnant women and their babies," it says.
Lung Foundation Australia says people with heart disease or failure, and those who've previously had a stroke can be "very seriously" affected.
What can you do to protect yourself from bushfire smoke?
Bayer said speaking with your GP to come up with a plan for dealing with smoke is a sensible step.
"For people living with lung health issues, it is important to work out a clear plan with your doctor for rapidly detecting and responding to any deterioration in symptoms," she said.
"Your plan should involve identifying and accessing cleaner air spaces – this can partially be achieved through closing doors and windows to minimise leakage into the house, or considering other indoor air quality purification like HEPA filters. "
Lung Foundation Australia lists a number of steps people should take if they're in an area that is "particularly affected" by bushfire smoke:
- Avoid physical activity outdoors (consider indoor activities instead)
- Rest more frequently
- Close windows and doors to minimise outside air coming into your home
- Switch your air conditioner (if you have one) to recycle or recirculate mode
- Follow your action plan and treatment advised by your doctor and keep your medicines close at hand
- Check the expiry dates and the supply of your commonly used medicines.
- Have your emergency plan ready in the event of an evacuation or the loss of essential services (such as power loss) during bushfires.
There are also masks available designed to filter out PM2.5 pollutants
