Breathing fire
Authors: None The Lancet Planetary Health
Journal: The Lancet Planetary Health (2021)

This year wildfires have rarely been out of the press. Since June, headlines have charted fires in Canada and the US Pacific northwest, Siberia, California, and countries around the Mediterranean, including Greece, Turkey, France, and Italy. At the time of writing, many of these fires continue to burn, and with the Australian bushfire season still to come, more such headlines might be expected. The increasing frequency and severity of wildfires over the past 40 years has been driven largely by the growing frequency of fire weather—the combination of hot, dry, and windy conditions—which, in the recently published IPCC Working Group I Sixth Assessment Report, was characterised as likely due to human influences and set to become still more common as the climate continues to heat. This issue of The Lancet Planetary Health includes a collection of four Articles exploring the health impacts of landscape fires, a term encompassing deliberately set fires (eg, for land management) as well as those that are not controlled. While the fires themselves cause widespread damage and threaten the lives of people fighting and fleeing them, it is the particulate matter in the smoke they produce that presents the greatest public health risk, and this is the focus of the collection. Gongbo Chen and co-authors give a global overview of these fires’ health impact by investigating deaths attributable to the acute effects of fire-related PM2·5 in 43 countries. Looking at acute exposures, they find increases of nearly 2% in cardiovascular, respiratory, and all-cause mortality per 10 μg/m3 of fire-related PM2·5. This is a larger health impact than conventional PM2·5, which they suggest could be due to greater toxicity or synergistic effects from wildfire smoke combining with other sources of ambient air pollution. Focusing on one of the countries most affected by wildfires, Tingting Le and co-authors look at the effects of short-term fire smoke exposure on emergency hospital admissions in Brazil. Accounting for background particulate matter emissions, they identify significant associations between fire smoke-related PM2·5 and respiratory and cardiovascular causes of hospital admissions, and greater vulnerability among the youngest and oldest members of the population. Despite the highest smoke-related PM2·5 exposures and health burden occurring in the states closest to the Amazon, the greatest number of attributable cases is actually in the highly populated southeast, highlighting the role of long-range atmospheric transport in spreading this risk across the country. The increased vulnerability of children and young people to the effects of fire-sourced PM2·5 poses a particular challenge in low- and middle-income countries, where most of the world's landscape fires occur. Tao Xue and co-authors describe how fire-sourced PM2·5 affects this vulnerable group using a sibling-matched case control study. They detect significant associations between child mortality and fire-sourced PM2·5, with effects increasing with the size of the fires. Between 2000 and 2014, the countries with the highest child mortality attributable to fire-sourced PM2·5 were Nigeria, the Democratic Republic of Congo, India, Uganda, and Indonesia—countries where such fires rarely make international headlines. Wildfires might seem like an inevitability, but there are ways to prepare for them and reduce the damage they cause, with the creation of firebreaks being one of the main tools. This is most easily achieved through controlled fires, also known as prescribed burns. However, these are not without their hazards. Nicolas Borchers-Arriagada and co-authors present a health impact assessment of fire-related PM2·5 in New South Wales, Australia, comparing the health costs from wildfires to those from prescribed burns. Wildfires have larger costs by far, they report, but those of prescribed burns are still substantial, and costs per hectare are higher, likely due to their closer proximity to population centres. These results emphasise the need to include all health impacts when weighing up the costs and benefits of different control measures. The papers in this collection illustrate some of the health challenges associated with landscape fires and the smoke they produce, how this can travel over long distances, and who is particularly vulnerable to smoke effects. With the frequency and intensity of these fires set to continue to grow, fire control measures will only become more important, but these too need rigorous evaluation. Rapidly and deeply cutting emissions will be crucial to minimising the severity of wildfires in the future, but with increasingly severe wildfires already with us, adapting to minimise risks and related injustices is a parallel challenge.