Exposure to the xenobiotic and AhR ligand benzo[a]pyrene, which directly binds to the AhR (Okey et al., 1984) and causes its nuclear localization, shortens the lifespan in mice (Sakakibara et al., 2005), and promotes neurodegeneration as well as Alzheimer’s disease and Parkinson’s disease-like phenotypes in zebrafish (Gao et al., 2015). The gene discussed is AHR; the disease is Parkinson disease.