Addressing Gaps in Age-Specific Evidence Used for United States Air Pollution Policy

Abstract

Background/Aim: Associations between air pollution and respiratory events in the U.S. have been estimated in multi-city studies using Medicare data. For populations not covered by Medicare (i.e., people under 65), evidence has relied on single-city studies. These studies may have limitations for informing national policy due to between-city differences in air pollution composition and population characteristics. Using emergency department (ED) data centralized by the U.S. Centers for Disease Control and Prevention’s National Environmental Public Health Tracking Program, we obtained the first multi-county effect estimates in the U.S. for respiratory ED visits across all ages. Methods: With 47.4 million respiratory ED visits, data included 894 U.S. counties for 2001–2012 (with 3 to 12 years per county). County-specific time-series analyses using quasi-Poisson log-linear models were conducted to estimate associations between air pollution and respiratory ED visits among children 0-<19, adults 19-<65, and adults 65 and older. We used ozone and fine particulate matter (PM2.5) concentration estimates from a Bayesian space-time downscaling fusion model. Overall health effect estimates were generated using a Bayesian approach to pool the county effect estimates. Results: In single pollutant models, we observed significant positive associations for respiratory ED visits and ozone for all age groups and PM2.5 for all age groups except for adults 65 and older. In two pollutant models, the association with ozone was greater among adults 19-< 65 (Rate Ratio [RR] 1.041 per 20 ppb, 95% Credible Interval [CI]: 1.036 – 1.047) than adults 65 and older (RR 1.034, 95% CI: 1.027 – 1.041) and no longer significant for children. For PM2.5, the association was higher among children (RR 1.029 per 10 µg/m³, 95% CI: 1.023 – 1.035) than adults 19-<65 (RR 1.008, 95% CI: 1.004 – 1.013). Conclusions: Our multi-county analyses covering people of all ages address a key gap in the evidence used to evaluate U.S. air pollution policy.