OBJECTIVES: Studies examining the combined health effects of both have been relatively lacking. We conducted a longitudinal study to investigate whether exposure to air pollutants and fungal spores might exacerbate childhood respiratory health. METHODS: Study participants were 100 elementary and middle-school students in Taipei County, Taiwan. A structured respiratory health questionnaire was administered in September 2007, followed by monthly spirometry from October 2007 to June 2008. During the study period, complete daily monitoring data for criteria air pollutants were obtained from the Environmental Protection Administration monitoring station and Aerosol Supersite. Fungal spores were measured from Sunday to Saturday in the week when lung-function measurements were made for each study month. Lung-function measurements were compared with air pollutants and fungal spores using mixed-effects models with 1-day-lag modeling. RESULTS: The particulate matter with an aerodynamic diameter of 2.5 mu m or less level 1 day before the lung function measurements was negatively associated with forced vital capacity. The fungal spore level was negatively associated with both forced expiratory vital capacity and forced expiratory volume in 1 second. O(3) level was negatively associated with forced expiratory flow at 25%, 50%, and 75% of forced vital capacity, and average expiratory flow over the middle half of forced vital capacity. CONCLUSIONS: This study suggested that exposure to particulate matter with an aerodynamic diameter of 2.5 mu m or less and fungal spores might cause adverse effects on the vital capacity of schoolchildren. Exposure to O(3) adversely affected small airway function. Pediatrics 2011;127:e690-e698