Global landscape fire-sourced ambient benzene and health risks in different future scenarios

Landscape fire (wildfire) has a detrimental impact on air quality and human health. However, the contribution of wildfire emissions to ambient benzene concentrations under future climate scenarios remains unknown. To effectively mitigate the adverse effects of wildfire, it is crucial to accurately capture the spatiotemporal trends of wildfire-related ambient benzene and its health impacts. In this study, the GEOS-Chem model was applied to simulate ambient fire-sourced benzene concentrations for 2015-2019 and 2045-2049 across four scenarios. Overall, global observed ambient benzene concentrations and simulated concentrations showed a correlation coefficient of 0.65, indicating robust model performance (p < 0.05). The wildfire-related ambient benzene concentration during 2015-2019 was 0.015 ± 0.011 (mean ± standard deviation) ppb, and then decreased through 2045-2049. Specifically, under the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios, the ambient benzene concentrations were projected at 0.005 ± 0.003, 0.008 ± 0.006, 0.009 ± 0.007, and 0.009 ± 0.007 ppb, respectively. These variations are closely linked to differences in the burned areas, fire activity, and fuel consumption. Wildfire-related ambient benzene concentrations showed significant seasonal variations with high concentrations in summer and autumn, and lower concentrations in winter. This seasonal pattern is likely associated with temperature fluctuations and varying fire activity. Spatially, tropical regions and the northern parts of the US, Canada, and Russia exhibited high wildfire-related ambient benzene concentrations. Although most regions are unaffected by marked carcinogenic or non-carcinogenic risks from ambient benzene, certain boreal and tropical countries remained at higher risks. To address this, better planning and design of natural and urban landscapes is essential to reduce wildfire occurrences, especially in wildfire hotspots. Additionally, controlling carbon emissions can significantly mitigate wildfire-related impacts on air quality.