The contribution of particulate matter to respiratory allergy

Background: Air pollution contributes to an estimated six million deaths per year. Epidemiological and experimental studies show an association between air pollutant exposure and respiratory allergy. Objective: We aimed to write a narrative review of the epidemiology of air pollution-related respiratory-related allergic disorders (including asthma and allergic rhinitis) and the effects of air pollutants - with an emphasis on the particulate matter - on respiratory allergy-related health. Methods: PubMed Medline was searched, and representative epidemiologic and controlled-exposure studies were selected by using terms for air pollutants, particulate matter, and respiratory allergy including asthma and allergic rhinitis. Results: Epidemiological studies showed methodologic heterogeneity, including variability in study populations, geographical regions, types and sources of pollutants, methods for exposure estimation, approaches to controlling for confounding, and case definitions. This heterogeneity affected measures of association between studies. There is strong evidence to support an association between exposure to particulate matter and asthmatic exacerbations. Although data are inconclusive, several studies suggest exposure to particulate matter contributes to the development of asthma, allergic sensitization, and allergic rhinitis. Experimental studies, such as controlled-exposure studies, support a causal association between particulate matter and adverse health effects. Conclusions: Particulate matter exposure can exacerbate pre-existing asthma and may contribute to developing asthma, allergic rhinitis, and aeroallergen sensitization. Short-term and long-term strategies are needed to reduce disease severity and prevent new-onset disease development. Additional research is needed to identify effective avoidance strategies and therapeutic approaches.