Seasonal and geographic effects on predicting personal exposure to nitrogen dioxide by time-weighted microenvironmental model

The purposes of this study were to investigate the impact of microenvironment concentrations on personal exposure by season and city, and to develop statistical models to predict personal exposure to nitrogen dioxide (NO2). Personal exposures, residential indoor, residential outdoor and workplace indoor levels of NO2 were measured in four cities in Korea (Seoul, Daegu, Asan and Suncheon) using a passive sampler for five weekdays. The measurements were conducted in summer and winter during 2008–2009. Average personal NO2 exposures were 20.5 ppb in summer and 18.6 ppb in winter. The average personal exposures of NO2 and residential indoor levels were the highest in Seoul and the lowest in Suncheon both summer and winter. Personal exposure was significantly different by season. Personal exposure was significantly correlated with residential indoor concentration in all cities. The personal exposure estimated by residential indoor, workplace indoor and outdoor levels explained 38% and 41% of the measured personal exposure variance in summer and winter, respectively. The low correlation may be due to the longer time spent in other microenvironments in the Korean population. Personal exposure was significantly correlated with working day and city. Correlation between the estimated personal exposure and measured personal exposure was significantly associated with the season and city. The model can provide reasonable estimation of population exposure with appropriate microenvironmental concentrations and time activity data. However, season- and city-specific models should be considered.