The Australian 2019/2020 bushfires and air quality – a summary of expert views and analyses

Francine Manansala
CASANZ President

2 February, 2020

The 2019/2020 Australian bushfires have brought widespread devastation to several parts of Australia destroying homes and resulting in losses of human life, flora and fauna. Another consequence of the bushfires is the prolonged effect they have had on air quality. The smoke from the fires has now travelled several thousand kilometres, to New Zealand and further afield. The past few months have seen an unprecedented level of media coverage relating to the air quality impacts of the bushfires and subsequent impact on health, generating considerable interest and debate. Many of our CASANZ members – who are experts in the field – have published scientific papers, have given interviews, and have publicly commented on the effects of the bushfires on air quality and health. Some of their findings and comments are summarised in this article.

Air Quality Trends

High temperatures and dry conditions have often been cited as factors that contributed to the bushfire crisis. Matthew Riley, CASANZ Certified Air Quality Professional and Director at the NSW Department of Planning Industry and Environment (DPIE), has been studying air quality trends in NSW for most of his career. In 2015, Matthew was interviewed by the Sydney Morning Herald regarding his department’s heatwave research and model projections. The projections, made out to 2030 and 2070, showed that the number of heatwave days was expected to increase by as much as 10 days per year by 2030 in northern NSW, with smaller increases predicted near the coast. “This provides a clear indication that, out to 2030, we can expect the heatwaves to happen more often, and for them to be longer. That’s likely to occur out to 2030, regardless of the emissions scenario”, Matthew said.

Matthew published an article on LinkedIn in December 2019 in relation to air quality from the bushfires quoting his DPIE colleague and air quality forecaster, Upma Dutt. Upma remarked that the conditions during the bushfire emergency were “unprecedented” with some days showing smoke, dust and ozone issues. Upma stated, “Because of the continuing drought, dust levels had already been high. The smoke from these massive bushfires combined with dust to create some of the worst particle pollution ever recorded in NSW, and to top it off ozone pollution in Sydney also spiked from the hot weather and increased nitrogen oxides and volatile organic compounds in the bushfire smoke”.

Matthew provided a data plot on LinkedIn (see below) of the population-weighted 24-hour average PM2.5 concentration in Sydney since the bushfires began in October 2019. The data show multiple days on which concentrations were above the WHO Guideline and Australian standard. Whilst Sydney experiences days over the standard from time to time, the number of elevated PM2.5 days recorded over the last few months is much greater than normal.

Source: Matthew Riley, LinkedIn

Indoor Air Quality

CASANZ Fellow and Director of the International Laboratory for Air Quality and Health, Professor Lidia Morawska was interviewed by ABC News in December 2019 regarding indoor air quality impacts from the bushfires. Professor Morawska stated, “Even with the windows closed, the difference in air quality could be … at most 10 to 25 per cent less concentrated”. She went on to say that fine particles from bushfire smoke could easily travel through structural leaks or cracks in buildings and, once inside, filtration would be the only way to improve air quality. Professor Morawska told Nine News that, “Air purifiers have been extensively used in some Asian countries which have regular events of severe air pollution. In some cases they were shown to help, but in other cases not so much because it really depends on the setting of the building”. She went on to say that air conditioners could improve indoor air quality in some cases, but the effectiveness would be dependent on whether the air conditioner brought air from outside to inside or not. The article noted that there have also been requests for the Australian government to consider establishing emergency shelters for sensitive people during extreme pollution events.

Face Masks

Since reports of air quality levels hit the headlines in late 2019, face masks have been flying off the shelves as residents try to protect themselves from the effects of bushfire smoke.

Lidia Morawska authored an article From face masks to air purifiers: what actually works to protect us from bushfire smoke?’ as a part of ‘The Conversation’ website in December 2019. She concluded that a mask is only effective if properly fitted and, if it isn’t, small particles (such as those from bushfires) can make their way through. She goes on to say that the effectiveness of such masks also depends on the behaviour of the wearer (e.g. how long it is worn and how often it is removed). Professor Morawska and Professor Wei Huang provide more information on face masks when used as protection from pollution in a 2019 article published in Nature journal.

CASANZ’s 2019 Clean Air Champion, Associate Professor at Tasmania’s Menzies Institute for Medical Research and Chief Investigator at CAR, Dr Fay Johnston, summarised the effectiveness of masks in an article for the ABC in December 2019. She said, “Face masks are the least useful measure, as a public health response. There’s only one sort that actually helps – that’s the P2 mask. They’re the only ones that can filter out a meaningful level of air pollution”. CAR has also released a factsheet called Bushfire smoke: what are the health impacts and what can we do to minimise exposure? In December 2019 which includes information regarding the use of P2/N95 masks.


Hospital admissions for respiratory-related issues have increased in recent months. We’ve also seen the cancellation of major entertainment, cultural and sporting events, such as New Year’s Eve firework displays and the Australian Open qualifiers.

The effects of short-term exposures to bushfire smoke are well known and studied, including in an Australian context. Dr Richard Broome, CASANZ member and NSW Health’s Director of Environmental Health, was quoted in an article on the NSW Health website in December 2019. “We know that combined effects of bushfire smoke and extreme temperatures have potential to cause severe illness, hospital admissions and even death. People with breathing conditions should avoid outdoor physical activity when there’s smoke around, and people with asthma should also follow their Asthma Action Plan and carry their relieving medication with them”, he said.

Dr Christine Cowie, CASANZ member and senior research fellow at the Centre for Air pollution, energy and health Research (CAR) at the University of NSW, was interviewed by the ABC and was asked about the long-term effects of medium-term exposures to bushfire smoke over weeks and months. She noted that breathing in a high amount of fine particles could affect physical development. “It is uncertain how medium-term exposure to these sporadic bushfire pollution events impact on long-term health. However, we do know that current evidence indicates there is no safe lower threshold of exposure to [particulate matter] pollution”, she said. Dr Cowie concluded that, whilst it is not easy to define what the exact health effects from prolonged bushfire smoke would be, it is recommended to take the normal health precautions. “Certainly, people who are repeatedly exposed to high levels [of air pollutants], and if they’re children for instance or elderly, it’s likely to impact on their lung function. No one can say definitively what happens after a two-month exposure to those high levels, other than if you’re susceptible, you’re likely to have increased respiratory problems”, she said. The Australian government has recently announced funding through the Medical Research Future Fund to address gaps in our knowledge about bushfire smoke exposure and health impact.

The New Zealand Perspective

CASANZ member and Senior Air Quality Analyst for Environment Canterbury in New Zealand Teresa Aberkane, provided some comments on the current air quality experience in Canterbury as a result of the Australian bushfires.

“In New Zealand we watch the images of the Australian fires on our screens with horror and compassion. Satellite images show the smoke carries a long way from original sources and under certain weather conditions it has reached parts of New Zealand. The MetService has received reports from Air NZ pilots of a layer of smoke ranging between 35,000 and 40,000 feet. These smoke particles filter out the blue light in the visible spectrum and can make the sky look orange and the sun look red, particularly at sunrise and sunset.

Some of these particles have come down to ground level. Particle concentrations in the air we breathe have been elevated on a few days and it is likely to have been from smoke from Australia. On 1 and 2 January, PM2.5 concentrations were elevated in seven Canterbury towns. The maximum daily average of 19 ug/m3 was measured at our monitoring site in Rangiora, about three times the concentrations during the previous few weeks. This is significantly less than what we experience in the middle of winter (max daily average 64 ug/m3), when wood is commonly burnt to heat our homes. While the concentrations on 1 and 2 January were minor compared to concentrations measured in Australia, this summer the visibility over and around Christchurch was clearly degraded on 1 and 2 January. It is a sad indicator of the scale of the bushfires that there may be an impact a couple of thousand kilometres from the source of the fires”.