AHR and Arthritis: Although this review focuses on the effects of PM and its constituents on autoimmune disease, it is worth noting that cigarette smoke also contains numerous PAHs at varying levels and there are several epidemiological studies that demonstrate an increased risk of autoimmune diseases such as RA, MS, and SLE in individuals who smoke cigarettes (180–185) and using animal models, Talbot et al. (116) demonstrated that cigarette smoke, which contains AHR ligands like PAHs, aggravates arthritis and increases the frequency of Th17 cells.