The Woolcock Institute of Medical Research

With winter upon us, it’s timely to consider our home heating choices and how they affect our health, says Dr Christine Cowie.

Were you aware that smoke from domestic wood heaters contributes disproportionately to wintertime air pollution, especially, but not only, in colder areas? The NSW EPA has estimated that wood heater emissions are the greatest contributor of larger and fine particulate matter (PM10 and PM2.5 respectively) in Sydney and the second greatest across the NSW greater metropolitan region (GMR) (Newcastle-Sydney-Illawarra) (NSW EPA, 2019).

Furthermore, in some parts of Sydney, the Department of Climate Change, Energy, the Environment and Water (DCCEEW, formerly DPIE) estimated that wood smoke can contribute up to about 3 µg/m3 PM2.5 exposure during winter (NSW DPIE, 2020), which is substantial given that mean annual exposure from 2010-2020 varied from approximately 5-9 ug/m3 (DPE 2022). This is alarming given that only five percent of Sydney households are reported to use wood heaters. So even in areas with a low proportion of wood heaters, these heaters disproportionately contribute to harmful air pollution.

With respect to health impact, a recent study estimated that in 2015 wood heater PM2.5 was associated with 728 premature deaths in Australia (Borchers-Arriagada et al., 2024), and there are varying estimates of premature deaths ranging from 100 deaths from earlier research (Broome et al., 2020) to 269 deaths (DPE, 2022) occurring each year in the NSW greater metropolitan region associated with exposure to woodsmoke PM2.5 pollution. More broadly, wood smoke is also associated with increased rates of asthma and other respiratory symptoms and an increased risk of heart and lung disease and premature deaths in the long-term.

You can access resources about the harmful effects of wood heater smoke and ways to reduce exposure or minimise emissions through the links below, but the best and safest option is replacement with an electrified source of heating, preferably powered by renewable energy.

While the above are estimates based on the best knowledge we have, there has been little direct research conducted into the impacts of wood smoke locally.

Researchers from the University of Canberra (Professor Sotiris Vardoulakis and Dr Nigel Goodman) and from the Woolcock (Dr Christine Cowie and Professors Guy Marks and Helen Reddel) have undertaken a pilot study to investigate whether the use of High Efficiency Particulate (HEPA) filtration air cleaners reduce levels of indoor PM2.5 pollution in homes with and without wood heaters, and whether their use leads to a change in respiratory symptoms of occupants.

The field work, which was completed during winter 2025, involved indoor and outdoor PM2.5 monitoring in 13 households, conducting breathing tests and collecting questionnaire and respiratory diary data from participants with asthma living in those households. Every two weeks the HEPA filters were added or removed from the air cleaners according to a randomisation schedule to enable “double blinding” (i.e., of participants and researchers). The study was conducted in the northwestern and western Sydney metropolitan area out to Blaxland in the lower Blue Mountains and involved five houses with wood heaters and eight houses using electric heating. The data from this study is currently being analysed and the results will be published and reported in future issues of the newsletter.

Find out more

• University of Canberra Wood Heater Smoke and Air Filtration Trial
• NHMRC Centre for Safe Air Wood Heater Smoke Fact Sheet
• NSW Health Department Wood Smoke Fact Sheet
• NSW EPA Tips for Reducing Wood Smoke Emissions
• Asthma Australia Wood Heating Fact Sheet
• Our Respiratory and Environmental Epidemiology research group
• Dr Christine Cowie