Global disparities in indoor wildfire-PM_2.5 exposure and mitigation costs

Wildfires have become more frequent and severe, and evidence showed that exposure to wildfire-caused PM_2.5 (fire-PM_2.5) is associated with adverse health effects. Fire-PM_2.5 exposure occurs mainly indoors, where people spend most of their time. As an effective and timely approach of mitigating indoor PM_2.5 pollution, air purifiers incur notable associated costs. However, the long-term global population exposure to indoor fire-PM_2.5 and the economic burden of using air purifiers remain unknown. Here, we estimated the indoor fire-PM_2.5 concentration and the cost of reducing indoor PM_2.5 exposure, along with the extra cost incurred because of fire-PM_2.5, at a resolution of 0.5° by 0.5° globally during 2003 to 2022. Our findings revealed 1009 million individuals exposed to at least one substantial indoor wildfire-air pollution day per year. We identified pronounced socioeconomic disparities in the costs of mitigating indoor PM_2.5 exposure, with low-income countries bearing a disproportionately higher economic burden, emphasizing the critical need for addressing these disparities.