Effect of air pollutants on respiratory symptoms and bronchodilator use among children, considering lags and cumulative exposure over several days (single pollutant models). OR's were calculated by using mixed models with random intercept for logistic regression, adjusting for sex, severity of asthma, atopy, minimum temperature during the previous day, and chronologic time. Symptom changes are shown with an increase of an interquartile range for each pollutant (1-hr O3 and 1-hr NO2 maximums, and 24-hr average for PM2.5) over several averages. * These models took into account records for symptoms at night, as well as pollution for the same day. Other models considered daily symptoms.