Association of daily asthma emergency department visits and hospital admissions with ambient air pollutants among the pediatric Medicaid population in Detroit: Time-series and time-stratified case-crossover analyses with threshold effects

► Association of asthma morbidity and concentrations of pollutants (with threshold) were studied. ► We focus on the pediatric Medicaid population of Detroit, Michigan, and performed both time-series and case-crossover analyses. ► Evidence of association was found for sulfur dioxide and fine particles (PM2.5). ► A significant threshold effect was found for PM2.5 at 11-13 μg m−3 using time-series and case-crossover methods. ► Effect estimates based on linear models (without thresholds) may underestimate the true risk. ► The findings were consistent across both types of designs.