Time-Lag Pattern of Short-Term Exposure to Traffic-Related Air Pollution and Changes in Exhaled Nitric Oxide in Asthmatic Children

摘要

Background/Aim: Short-term exposure to traffic-related air pollution (TRAP) has been associated with asthma exacerbation and increases in exhaled nitric oxide (FeNO), a biomarker of airway inflammation, with time lags ranging from several hours to a few days. Very few studies have examined TRAP-FeNO associations on less than 24-hour timescale. Moreover, most of the previous studies have used central-site exposure data. We aimed to investigate the lag structure of changes in FeNO in response to black carbon (BC), a marker for diesel exhaust particulate matter exposure, at hourly resolution measured by personal monitors from 35 asthmatic children in seaport-adjacent communities in New Jersey. Methods: Thirty five children with mild-to-moderate physician-diagnosed asthma wore micro-aethalometers (AE51, Aethlabs) for around 30 days (1071 observations in total). FeNO was measured daily in late afternoon using a NIOX MINO. Linear-mixed effect model was applied to quantify the BC-FeNO association after adjusting for day-of-week, temperature, age and gender. The lag was stratified as every two hours within 24-hour before the time of FeNO measurement. Results: Based on data from the first 9 subjects, FeNO level was positively associated with 24-hour average BC exposure (0.69% [95%CI: -1.62%, 3.05%] per one μg/m3 increase in BC) in the adjusted model. However, we observed inverse associations between BC and FeNO within 24 hour prior to FeNO measurement, and the association was strongest at lag 14-16 hours (-5.5% [95%CI: -9.38%, -1.44%] per one ug/m3 increase in BC) The strength of negative associations increased from lag 4-6 hours to lag 16-18 hours, and then decreased and becoming positive, over lags 18-20, 20-22 and 22-24 hours. Conclusions: Given the known high spatial and temporal variation in exposure to TRAP, the preliminary results support the need for further study of time-lag patterns between exposure to TRAP and acute asthma outcomes.