With state and private landowners taking advantage of mild autumn conditions to conduct controlled burns, public health experts are warning of risks posed by smoky days and the need to protect lungs.
Controlled burning around Perth is "absolutely critical" to preventing out-of-control summer bushfires, according to Murray Carter, executive director of the rural fire division of the Department of Fire and Emergency Services (DFES).
And that can mean smoke haze around the metropolitan area.
"We don't always get as good conditions as we've got now [for burning]," Mr Carter told Nadia Mitsopoulos on ABC Radio Perth.
He said conditions were ideal for cool burning, which attempted to reduce the fuel load in the landscape before the summer bushfire season started.
"We're really seasonally dependent on how much we can get in, but the more burning that we can get in under these cooler conditions, under cool burning conditions, you're much better placed to be able to effectively manage uncontrolled wildfires when they occur in summer," Mr Carter said.
Numerous burns lead to lots of smoke
Mr Carter said several agencies were taking advantage of the mild weather to conduct controlled burning this week.
"We have agencies such as ours doing some work on crown land, we have local governments burning, Parks and Wildlife are very active because the season's right to do that," he said.
But he acknowledged the cumulative effect was a lot of smoke across the metropolitan area.
"It's not that the burns produce more [smoke], there's just a fair bit of it going on because the conditions are really highly acceptable for it now," Mr Carter said.
Alarm about respiratory effects
While the burning is intended to lower the risk of devastating wildfires in summer, some people are sounding the alarm about the public health impacts of the smoke.
Sajni Gudka from the University of WA's School of Population and Global Health said she was concerned not enough was being done to warn the public about the dangers of breathing in smoke, especially on days when it was particularly heavy.
She said Tuesday's air quality index in Perth was at a hazardous level.
"I and a few people that I've spoken to said they woke up at around four or five o'clock in the morning with difficulties breathing," Dr Gudka said.
"[They were] having to use their inhalers, closing windows and doors, putting towels under the doorframes to keep the smoke out of their house, because they were having breathing difficulties."
She said it was the quantity of particulate matter (PM) — essentially tiny fragments of ash — that people should be most concerned about.
"In this case, what we're talking about is PM2.5, which is a combination of organic and inorganic substances like nitrates, sulphates and metals such as iron, copper, nickel — they form particulates, which we call particulate matter.
"When we looked at the air quality [on Tuesday], we saw that the PM2.5 in the Perth air shed — the air we breathe — was almost eight, nine times higher than the World Health Organization guidelines have for recommended air quality.
"It then causes a series of breathing difficulties, headaches, high blood pressure in people at various moments throughout the time that they're breathing that PM2.5."
Could masks offer protection?
Dr Gudka said some masks being worn for protection against COVID-19 could also filter out some PM particles.
While cloth and surgical masks would not offer much protection, some N95 masks and PM2 masks would filter out the larger particles, she said.
"The microparticles, which are PM0.1, will get through that N95 mask or your PM2.5 filter."
She said she also wanted to see greater public health messaging.
"I know some people who will, as a result of Tuesday's smoke, probably take three, four or five days for their lungs to recover to fully back to normal.
"There has to be some better messaging around this.
'It spoils the best time of the year'
Listeners to ABC Radio Perth said the heavy smoke haze had left them struggling for breath.
"The smoke is affecting me badly today and my lung condition is mild. A bit of warning would be nice. I would have shut all the windows. I hate to think how people with a more serious condition are coping." — Susie
"I had the window open last night and woke up choking. I couldn't sleep for the rest of the night. Exacerbated my mild asthma and having an ear and throat infection doesn't help. Effectively this happens right throughout spring and autumn. I know we need to burn off heavy fuel loads, but it needs to be better managed." — John
"The most awful thing about the prescribed burning, apart from asthma, is it's always when we get this superb autumn weather. It spoils the best time of the year … there must be a better way." — Nel
