In recent years, with the intensification of global warming, the frequency of wildfires (referring to uncontrolled or unplanned fires burning in wildland vegetation) has been increasing globally, posing a serious threat to the environment and public health. The smoke produced by wildfires can cause severe air pollution, often affecting areas hundreds or even thousands of kilometers away. The impact on populations and the health risks posed far exceed the fire itself. Therefore, tracking population exposure to wildfire-related air pollution (primarily particulate matter with a diameter of less than 2.5 micrometers [PM_2.5] and secondary pollutants like ozone [O₃]) is crucial for monitoring and managing its health impacts and implementing targeted prevention and intervention measures.

On September 20, 2023, a study titled "Global population exposure to landscape fire air pollution from 2000-2019" was published online in Nature (https://doi.org/10.1038/s41586-023-06398-6). This research was a collaboration between Monash University in Australia, Nanjing University of Information Science & Technology, and other institutions. The study collected data from multiple sources, including air pollution data from ground-level air quality monitoring stations, fire source PM_2.5 and O₃ concentrations simulated by the GEOS-Chem atmospheric chemistry transport model, and high-resolution meteorological reanalysis data. It estimated the daily concentrations of fire source PM_2.5 and O₃ from 2000 to 2019 globally at a spatial resolution of 0.25°×0.25° (approximately 28km×28km grid), and conducted a systematic assessment of global population exposure to fire source PM_2.5 and O₃ by combining this with high-resolution population distribution data.

The study found that global exposure to fire source PM_2.5 increased overall during 2000-2019, while the trend for fire source O₃ was not clear. Central Africa, South America, Siberia, and Southeast Asia were particularly affected by fire-related air pollution. Between 2010 and 2019, on average, each person globally was exposed to significant fire-related air pollution (SFAP) for 9.9 days per year, with a total of 2.18 billion people being exposed to SFAP for at least one day per year. The total annual exposure days reached 72.8 billion, showing increases compared to 2000-2009. There were noticeable socio-economic disparities in exposure to fire-related air pollutants. The annual population-weighted average concentrations of fire source PM_2.5 and O₃ in low-income countries were more than four times higher than in high-income countries. The regions with the highest population-weighted average concentrations of fire source PM_2.5 and O₃ were in Central African countries (such as the Democratic Republic of the Congo and Angola), where the number of days per person per year exposed to SFAP was also the highest globally, reaching up to 100 or more days, with a maximum of 150 days. Therefore, the international community needs to pay more attention to these low- and middle-income countries to reduce the health inequities caused by fire-related air pollution.

This study was mainly conducted by Monash University in Australia and Nanjing University of Information Science & Technology. Professor Xu Yue from the School of Environmental Science and Engineering at Nanjing University of Information Science & Technology, Professor Yuming Guo, and Associate Professor Shanshan Li from the School of Public Health and Preventive Medicine at Monash University were the co-corresponding authors. Dr. Rongbin Xu from the School of Public Health and Preventive Medicine at Monash University was the first author of the paper.