Abstract
Indoor and outdoor NO2 concentrations were measured and compared simultaneously with personal NO2 exposures for 25 university students for 2 days each on weekdays and weekends. House characteristics and activity patterns were used to determine the impacts of these factors on personal exposure. During the 48-hour monitoring period, mean indoor and outdoor NO2 concentrations were 26.1 ppb and 32.9 ppb on weekdays, respectively, and personal exposure was 29.7 ppb. While mean indoor and outdoor NO2 concentrations on weekends were 38.1 ppb and 39.6 ppb respectively personal exposure was 44.3 ppb. Since university students spent most of their time indoors, their NO2 exposures were associated with indoor NO2 levels rather than outdoor NO2 levels both weekdays and weekends in spite of different time activity patterns. Using a time-weighted average model, personal NO2 exposures of the university students were estimated by NO2 measurements indoors at home, indoors at school, and outdoors at home. Estimated personal NO2 exposures were significantly correlated with measured personal NO2 exposures (Spearman r =0.72). However, estimated personal NO2 exposures by the time-weighted average model were significantly underestimated, compared with the measured personal NO2 exposures. This suggests that the personal NO2 exposure of university students is affected by other factors such as transportation.
