Abstract
Rationale: Ultrafine particle (UFP; particles <0.1 μm in diameter) concentrations exhibit high spatiotemporal variability; thus, individual-level exposures and health risks are difficult to estimate. Objectives: To determine the effects of recent UFP exposures on respiratory health outcomes in children and to determine if children with asthma are at increased risk. Methods: Personal sampling of UFPs was completed by adolescents in combination with repeated personal spirometry measurements and ecological momentary assessment of respiratory symptoms (wheeze, cough, and/or shortness of breath). We assessed the association between UFP exposures every 30 minutes up to 150 minutes before measuring forced expiratory volume in 1 second (FEV(1)), peak expiratory flow, and respiratory symptoms using mixed-effects models and interaction with asthma diagnosis. Results: Participants (N = 105; 43% with asthma) completed an average of 11 spirometry measurements and 16 symptom responses throughout sampling. After adjustments (maternal education, physical activity, season, and distance to nearest roadway), a 10-fold increase in UFP exposure was significantly associated with a 0.04-L decrease (95% confidence interval [CI], -0.07 to -0.001) in FEV(1) 90 minutes later. Asthma status modified this association in which participants with asthma had significantly lower FEV(1) values in response to UFP exposures 30 minutes earlier than participants without asthma. We found a significant increase in the odds of reporting a respiratory symptom 30 minutes after increased UFP exposure (odds ratio, 1.8; 95% CI, 1.00 to 3.00). Conclusions: Greater UFP exposure conferred deleterious effects on lung function and respiratory symptoms within 90 minutes of exposure and was more pronounced among participants with asthma.