Air pollution, urgent asthma medical visits and the modifying effect of neighborhood asthma prevalence

Background: Social and environmental stressors may modify associations between environmental pollutants and asthma symptoms. We examined if neighborhood asthma prevalence (higher: HAPN vs. lower: LAPN), a surrogate for underlying risk factors for asthma, modified the relationship between pollutants and urgent asthma visits. Methods: Through zip code, home addresses were linked to New York City Community Air Survey’s land use regression model for street-level, annual average nitrogen dioxide (NO ₂ ), particulate matter (PM _2.5 ), elemental carbon (EC), summer average ozone (O ₃ ), winter average sulfur dioxide (SO ₂ ) concentrations. Poisson regression models were fit to estimate the association (prevalence ratio, PR) between pollutant exposures and seeking urgent asthma care. Results: All pollutants, except O ₃ were higher in HAPN than LAPN (P < 0.01). Neighborhood asthma prevalence modified the relationship between pollutants and urgent asthma (P-interaction < 0.01, for NO ₂ and SO ₃ ). Associations between pollutants and urgent asthma were observed only in LAPN (NO ₂ : PR = 1.38, P = 0.01; SO ₃ : PR = 1.85, P = 0.04). No association was observed between pollutants and urgent asthma among children in HAPN (P > 0.05). Conclusions: Relationships between modeled street-level pollutants and urgent asthma were stronger in LAPN compared to HAPN. Social stressors that may be more prevalent in HAPN than LAPN, could play a greater role in asthma exacerbations in HAPN vs. pollutant exposure alone.