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 versus pollutant exposure alone.