Global wildfire emissions and health impacts

Wildfire smoke is an increasingly serious threat to climate, air quality, and public health as extreme fires, transboundary transport, and population exposure intensify. This Review synthesizes advances in satellite remote sensing, emission inventories, chemical transport modeling, epidemiology, and toxicology in the fire-smoke-health chain. Emission factor evidence indicates that fine particle emissions generally decline with increasing combustion efficiency, but this relationship varies by fuel, burning condition, and measurement design. Recent global health impact assessments report substantial mortality burdens from landscape fire emissions, including model-based estimates of approximately 1.5 million annual excess deaths during 2000–2019, with large regional inequities. However, comparisons remain limited by differences in inventories, plume injection, chemistry, exposure metrics, and concentration-response functions. Toxicological evidence suggests that wildfire smoke may differ from urban and other particles through organic composition, oxidative potential, aging, and wildland-urban interface material burning, but mechanisms remain unresolved. Future progress requires exposure-weighted measurements, validated smoke attribution, composition-linked health studies, and equitable interventions. Broader context: Wildfire smoke is no longer only a local fire season hazard. Climate change, land use pressure, and expansion of communities into fire prone landscapes are increasing smoke exposure near fires and far downwind. This Review connects the end-to-end evidence chain from emission factors and satellite-based inventories to atmospheric transport, source attribution, and health burden, thereby clarifying why health estimates differ across studies. Key sources of uncertainty include the omission of small fires, misplaced smoke plumes, toxicity changes during chemical aging, and different assumptions adopted in risk models. Better smoke risk governance requires more comparable fire emission inventories, exposure models that capture peaks and vulnerable populations, interventions (e.g., early warnings, clean air shelters, indoor filtration), and safer planning in the wildland-urban interface.