Rationale: Air pollution is a known asthma trigger and has been associated with short-term asthma symptoms, airway inflammation, decreased lung function, and reduced response to asthma rescue medications. Objectives: To assess a causal relationship between air pollution and childhood asthma using data that address temporality by estimating air pollution exposures before the development of asthma and to establish the generalizability of the association by studying diverse racial/ethnic populations in different geographic regions. Methods: This study included Latino (n ¼ 3,343) and African American (n ¼ 977) participants with and without asthma from five urban regions in the mainland United States and Puerto Rico. Residential history and data from local ambient air monitoring stations were used to estimate average annual exposure to five air pollutants: ozone, nitrogen dioxide (NO 2 ), sulfur dioxide, particulate matter not greater than 10 mm in diameter, and particulate matter not greater than 2.5 mm in diameter. Within each region, we performed logistic regression to determine the relationship between early-life exposure to air pollutants and subsequent asthma diagnosis. Arandom-effectsmodelwasusedtocombinetheregionspecific effects and generate summary odds ratios for each pollutant. Measurements and Main Results: After adjustment for confounders, a 5-ppb increase in average NO 2 during the first year of life was associated with an odds ratio of 1.17 for physician-diagnosed asthma (95% confidence interval, 1.04-1.31). Conclusions: Early-life NO 2 exposure is associated with childhood asthma in Latinos and African Americans. These results add to a growing body of evidence that traffic-related pollutants may be causally related to childhood asthma.

Black and Latino children had worse asthma status and less use of preventive asthma medications than white children within the same managed Medicaid populations. Most other processes of asthma care seemed to be equal or better for minorities in the populations that we studied. Increasing the use of preventive medications is a natural focus for reducing racial disparities in asthma.

Underuse of controller medications among Medicaid-insured children is widespread. Racial minorities and children whose parents are less educated are at higher risk for underuse. Patients who have received action plans or had follow-up visits or specialty consultations are less likely to be symptomatic underusers of controller medications.