Acute Effects of Ambient Air Pollution on Asthma Emergency Department Visits in Ten U.S. States

BACKGROUND: Previous studies of short-term ambient air pollution exposure and asthma morbidity in the United States have been limited to a small number of cities and/or pollutants and with limited consideration of effects across ages. OBJECTIVES: To estimate acute age group-specific effects of fine and coarse particulate matter (PM), major PM components, and gaseous pollutants on emergency department (ED) visits for asthma during 2005–2014 across the United States. METHODS: We acquired ED visit and air quality data in regions surrounding 53 speciation sites in 10 states. We used quasi-Poisson log-linear time-series models with unconstrained distributed exposure lags to estimate site-specific acute effects of air pollution on asthma ED visits overall and by age group (1–4, 5–17, 18–49, 50–64, and [Formula: see text] y), controlling for meteorology, time trends, and influenza activity. We then used a Bayesian hierarchical model to estimate pooled associations from site-specific associations. RESULTS: Our analysis included [Formula: see text] asthma ED visits. We observed positive associations for multiday cumulative exposure to all air pollutants examined [e.g., 8-d exposure to [Formula: see text]: rate ratio of 1.016 with 95% credible interval (CI) of (1.008, 1.025) per [Formula: see text] increase, [Formula: see text]: 1.014 (95% CI: 1.007, 1.020) per [Formula: see text] increase, organic carbon: 1.016 (95% CI: 1.009, 1.024) per [Formula: see text] increase, and ozone: 1.008 (95% CI: 0.995, 1.022) per [Formula: see text] increase]. [Formula: see text] and ozone showed stronger effects at shorter lags, whereas associations of traffic-related pollutants (e.g., elemental carbon and oxides of nitrogen) were generally stronger at longer lags. Most pollutants had more pronounced effects on children ([Formula: see text] y old) than adults; [Formula: see text] had strong effects on both children and the elderly ([Formula: see text] y old); and ozone had stronger effects on adults than children. CONCLUSIONS: We reported positive associations between short-term air pollution exposure and increased rates of asthma ED visits. We found that air pollution exposure posed a higher risk for children and older populations. https://doi.org/10.1289/EHP11661