AbstractIn this review, we identified 15 studies in children and 10 studies in adults that assessed the association between long-term exposure to air pollution and incident asthma and that conducted stratified analyses to explore potential suscep-tibility factors. Overall, adult never-/former smokers seem to be at higher risk of incident asthma due to air pollution. Children without atopy and children from low socioeconomic status families also seem to be at higher risk of incident asthma due to air pollution. While interaction between air pollution and genes involved in the response to oxidative stress path-ways have been explored, results are somewhat inconsistent and in need of replication. To evaluate interactions, large sam-ple sizes are necessary, and much more research, including data pooling fromexisting studies, is needed to further explore susceptibility factors for asthma incidence due to long-termair pollution exposure. KeywordsAir pollution.Incident asthma .Susceptibility factors .Long-termexposure