The Australian 2019/2020 bushfires were unprecedented in both their extent and intensity, causing a catastrophic loss of habitat and human and animal life across eastern-Australia. Between October 2019 and February 2020 hundreds of fires burned, peaking in size in December and January and releasing the equivalent of half of Australia’s annual carbon dioxide (CO2) emissions. We use a high-resolution atmospheric-chemistry transport model to assess the impact of the bushfires on particulate matter with a diameter less than 2.5 µm (PM2.5) concentrations across eastern Australia. The health burden from short-term population exposure to PM2.5 is then quantified using a concentration response function. We find that between October and February an additional ~1.9 million people in eastern-Australia were exposed to ‘Poor’, ‘Very Poor’ and ‘Hazardous’ air quality index levels due to the fires. The impact of the bushfires on AQ was concentrated in the cities of Sydney, Newcastle-Maitland and Canberra-Queanbeyan during November, December and, also in Melbourne, in January. The health burden of bushfire PM2.5 across eastern-Australia, regionally and at city level is also estimated. Our estimate indicates that between October and February 171 (95% CI: 66 – 291) deaths were brought forward. The health burden was largest in New South Wales (109 (95% CI: 41 – 176) deaths brought forward), Queensland (15 (95% CI: 5 – 24)) and Victoria (35 (95% CI: 13 – 56)). At a city level the health burden was concentrated in Sydney (65 (95% CI: 24 – 105)), Melbourne (23 (95% CI: 9 – 38)) and Canberra-Queanbeyan (9 (95% CI: 4 – 14)), where large populations were exposed to high PM2.5 concentrations due to the bushfires.

Forest and vegetation fires, used as tools for agriculture and deforestation, are a major source of air pollutants and can cause serious air quality issues in many parts of Asia. Actions to reduce fire may offer considerable, yet largely unrecognised, options for rapid improvements in air quality. In this study, we used a combination of regional and global air quality models and observations to examine the impact of forest and vegetation fires on air quality degradation and public health in Southeast Asia (including Mainland Southeast Asia and south-eastern China). We found that eliminating fire could substantially improve regional air quality across Southeast Asia by reducing the population exposure to fine particulate matter (PM2.5) concentrations by 7% and surface ozone concentrations by 5%. These reductions in PM2.5 exposures would yield a considerable public health benefit across the region; averting 59,000 (95% uncertainty interval (95UI): 55,200-62,900) premature deaths annually. Analysis of subnational infant mortality rate data and PM2.5 exposure suggested that PM2.5 from fires disproportionately impacts poorer populations across Southeast Asia. We identified two key regions in northern Laos and western Myanmar where particularly high levels of poverty coincide with exposure to relatively high levels of PM2.5 from fires. Our results show that reducing forest and vegetation fires should be a public health priority for the Southeast Asia region.

Wildfires result in human fatalities not only due to the direct exposure to flames, but also indirectly through smoke inhalation. The Mediterranean basin with its hot and dry summers is a hotspot for such devastating events. The situation has further been aggravated in recent years by climate change as well as a growing and aging population in the region. To assess the health impacts due to short-term exposure to air pollution created by the 2021 summer wildfires in the eastern and central Mediterranean basin, we used a regional-scale chemistry transport model to simulate concentrations of major air pollutants such as fine particulate matter with a diameter less than 2.5 μm (PM2.5), SO2, NO2, and O3 - in a fire and a no-fire scenario. Elevated short-term exposure of the population to air pollutants are associated with excess all-cause mortality using relative risks for individual pollutants from previously published meta-analyses. Our estimates indicate that the short-term exposure to wildfire-caused changes in O3 accounted for 741 (95% CI:556-940) excess deaths in total over the entire region of investigation during the wildfire season between mid-July to early October 2021. This is followed by 270 (95% CI:177-370) excess deaths due to elevated PM2.5 exposure, rendering the health effect of increased O3 from wildfires larger than the effect of increased PM2.5. We show this to be attributed largely to the spatially more widespread impact of wildfires on O3. Our study concludes with a discussion on uncertainties associated with the health impact assessment based on different air pollutants.