Bushfires have always been a feature of the natural environment in Australia, but the risk has increased over time as fire seasons start earlier, finish later, and extreme fire weather (ie, very hot, dry and windy conditions that make fires fast moving and very difficult to control) becomes more severe with climate change.1,2,3 The 2019–20 bushfires in Australia, particularly in New South Wales, Victoria, Queensland and the Australian Capital Territory, have caused at least 33 fatalities, extensive damage to property and destruction of flora and fauna, and have exposed millions of people to extreme levels of air pollution. Bushfire smoke, as well as smoke from prescribed burns, contains a complex mixture of particles and gases that are chemically transformed in the atmosphere and transported by the wind over long distances.4 In this context, a major public health concern is population exposure to atmospheric particulate matter (PM) with a diameter < 2.5 μm (PM2.5), which can penetrate deep into the respiratory system, inducing oxidative stress and inflammation,5 and even translocate into the bloodstream.6
Such exposure can adversely affect health outcomes. Mortality rates have been found to increase in Sydney on days with high bushfire smoke pollution.7 Hospital admissions, emergency department attendances, ambulance call‐outs and general practitioner consultations, particularly for respiratory conditions, all increase during periods of severe PM2.5 levels from bushfires.8,9,10,11 The risks from air pollution are amplified when combined with high temperatures during heatwaves, with an increased effect on mortality.12
Certain population groups are at higher risk from exposure to smoke, either because they typically breathe in more air per bodyweight and their organs are still developing (young children), spend more time outdoors (outdoor workers, homeless people), or are more vulnerable to smoke due to old age or a pre‐existing health condition (asthma, chronic obstructive pulmonary disease or other respiratory condition, cardiovascular illness, or diabetes). There is evidence that exposure to bushfire smoke during pregnancy is associated with reduced birthweight in babies and a higher risk of gestational diabetes in mothers.13,14 People in lower socio‐economic groups are potentially at higher risk, as they may have poorer housing, and lower health literacy and ability to take preventive measures.