Despite attempts and some successes to improve air quality over the decades, current U.S. national trends suggest that exposure to outdoor and indoor air pollution remains a significant risk factor for both the development of asthma and the triggering of asthma symptoms. Emerging science also suggests that environmental exposures during the prenatal period and early childhood years increase the risk of developing asthma. Multiple mechanisms mediate this risk as a wide range of deleterious air pollutants contribute to the pathogenesis of asthma, across a variety of complex asthma phenotypes. In this review, we will consider the role of altered innate and adaptive immune responses, gene by environment interactions, epigenetic regulation, and possibly gene by environment by epigene interactions. Gaining a greater understanding of the mechanisms that underlie the impact of exposure to air pollution on asthma, allergies, and other airway diseases can identify targets for therapy. Such interventions will include pollutant source reduction amongst those most exposed and most vulnerable, and novel pharmaceutical strategies to reduce asthma morbidity
