K Berhane, ML Chang, R McConnell. JAMA. 2017;315(14):1491–1501 Exposure to elevated concentrations of ambient air pollutants is associated with increases in the prevalence of bronchitic symptoms in children. The authors hypothesized that reductions in measured air pollutants over the periods studied would be associated with an improvement in respiratory symptoms in children with or without asthma. Data were collected from 3 successively recruited cohorts involving 4602 children (48% female subjects, age range of 5–18 years, mean age of 8 years, 45% Hispanic) from 8 Southern California communities during the years 1993 to 2001, 1996 to 2004, and 2003 to 2012. This was a longitudinal study with data from the 3 separate …