Health effects of wildfire smoke

As part of the Cités team, we are currently conducting several projects on the impact of fine particulate matter from wildfires on mortality and hospitalizations in France. In particular, we are seeking to understand how these risks vary across regions and among different population subgroups, in order to highlight potential social and regional health inequalities linked to these events. Our research takes an environmental justice perspective: the goal is to identify which populations are most exposed to and vulnerable to wildfire risk, with the aim of prioritizing prevention measures for these populations.

Our team, which has already conducted research on this topic in North America, particularly in California, has previously demonstrated that:

• In California, smoke from wildfires has a greater impact on respiratory health than fine particulate matter from other sources (Aguilera R, Corringham T, Gershunov A, Benmarhnia T. Wildfire smoke impacts respiratory health more than fine particles from other sources: observational evidence from Southern California. Nat Commun. 2021 Mar 5;12(1):1493. doi: 10.1038/s41467-021-21708-0)
• This finding was confirmed in a study conducted in Europe: the associations with mortality were stronger for PM2.5 linked to wildfires than for PM2.5 not linked to wildfires (Alari A, Ballester J, Milà C, Benmarhnia T, Sofiev M, Uppstu A, Hänninen R, Tonne C. Quantifying the short-term mortality effects of wildfire smoke in Europe: a multicountry epidemiological study in 654 contiguous regions. Lancet Planet Health. 2025 Aug;9(8):101296. doi: 10.1016/j.lanplh.2025.101296)
• Wildfire smoke does not affect everyone’s health in the same way: certain subgroups are particularly at risk (Letellier N, Jones-Ngo CG, Cheung MW, Aguilera R, Casey JA, Zakaras JM, Sugrue R, Teherani A, Thakur N, Collard H, Weiser SD, Benmarhnia T. Using generalized random forests to characterize vulnerability to adverse health outcomes following wildfire smoke exposure in California. Environ Int. 2025 Dec;206:109955. doi: 10.1016/j.envint.2025.109955)
• Beyond the short-term effects, it is also essential to characterize and study the long-term effects of repeated exposure to these pollutants, which may be unevenly distributed across the population and may have adverse health consequences (Casey JA, Kioumourtzoglou MA, Padula A, González DJX, Elser H, Aguilera R, Northrop AJ, Tartof SY, Mayeda ER, Braun D, Dominici F, Eisen EA, Morello-Frosch R, Benmarhnia T. Measuring long-term exposure to wildfire PM_2.5 in California: Time-varying inequities in environmental burden. Proc Natl Acad Sci U S A. 2024 Feb 20;121(8):e2306729121. doi: 10.1073/pnas.2306729121).