Background Emerging evidence suggests that traffic-related air pollution (TRAP) is associated with childhood asthma. However, no studies have estimated the burden of childhood asthma attributable to TRAP for the United States. We aimed to estimate the number of incident childhood asthma cases attributable to Nitrogen Dioxide (NO2) - a good marker of TRAP - in the Contiguous U.S. for the years 2000 and 2010. Methods Using a published national regression model, we estimated NO2 exposures at the centroid of each U.S. Census Block and assigned that exposure to all children (birth -18 years old) living in that Block. From the literature, we extracted a national average asthma incidence rate of 12.5 per 1,000 at-risk children/year and a concentration-response function of 1.05 (95% CI = 1.O2, 1.07) per 4 μg/m3 NO2. We calculated the relative risk, population attributable fraction and number of childhood asthma cases attributable to NO2 exposures at each Census Block using a standard burden of disease assessment framework. We summed the attributable number of childhood asthma cases across the Contiguous U.S. Results NO2 accounted for 209,058 (27%) incident cases of childhood asthma in 2000 and 141,931 (18%) in 2010. The reduction of cases was mainly due to a documented reduction in average NO2 concentrations between 2000 and 2010 (18.7 μg/m3 to 11.9 μg/m3). In current work, we are repeating this analysis with state-specific asthma incidence rates and with exposure to other pollutants including PM2.5 and PM10. Conclusion A considerable proportion of new childhood asthma cases are attributable to NO2 in the Contiguous U.S. We expect that TRAP-related cases would be preventable if TRAP emissions were reduced.
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