Global population exposure to landscape fire air pollution from 2000 to 2019

Wildfires are thought to be increasing in severity and frequency as a result of climate change^1-5. Air pollution from landscape fires can negatively affect human health^4-6, but human exposure to landscape fire-sourced (LFS) air pollution has not been well characterized at the global scale^7-23. Here, we estimate global daily LFS outdoor fine particulate matter (PM_2.5) and surface ozone concentrations at 0.25° × 0.25° resolution during the period 2000-2019 with the help of machine learning and chemical transport models. We found that overall population-weighted average LFS PM_2.5 and ozone concentrations were 2.5 µg m^-3 (6.1% of all-source PM_2.5) and 3.2 µg m^-3 (3.6% of all-source ozone), respectively, in 2010-2019, with a slight increase for PM_2.5, but not for ozone, compared with 2000-2009. Central Africa, Southeast Asia, South America and Siberia experienced the highest LFS PM_2.5 and ozone concentrations. The concentrations of LFS PM_2.5 and ozone were about four times higher in low-income countries than in high-income countries. During the period 2010-2019, 2.18 billion people were exposed to at least 1 day of substantial LFS air pollution per year, with each person in the world having, on average, 9.9 days of exposure per year. These two metrics increased by 6.8% and 2.1%, respectively, compared with 2000-2009. Overall, we find that the global population is increasingly exposed to LFS air pollution, with socioeconomic disparities.