Abstract
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 synthesises advances in satellite remote sensing, emission inventories, chemical transport modelling, 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 WUI material burning, but mechanisms remain unresolved. Future progress requires exposure-weighted measurements, validated smoke attribution, composition-linked health studies, and equitable interventions.