Otitis media (OM) is one of the most common early childhood infections, resulting in an enormous economic burden to the health care system through unscheduled doctor visits and antibiotic prescriptions. Zemek et al. (p. 1631) investigated the association between ambient air pollution exposure and emergency department (ED) visits for OM using 10 years of ED data from Edmonton, Alberta, Canada, and measures of carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), sulfur dioxide, and particulate matter (PM; median aerometric diameter ? 10 and 2.5