Different relationships between personal exposure and ambient concentration by particle size.

Ambient particulate matter (PM) concentrations at monitoring stations were often used as an indicator of population exposure to PM in epidemiological studies. The correlation between personal exposure and ambient concentrations of PM varied because of diverse time-activity patterns. The aim of this study was to determine the relationship between personal exposure and ambient concentrations of PM10 and PM2.5 with minimal impact of time-activity pattern on personal exposure. Performance of the MicroPEM, v3.2 was evaluated by collocation with central ambient air monitors for PM10 and PM2.5. A field technician repeatedly conducted measurement of 24 h personal exposures to PM10 and PM2.5 with a fixed time-activity pattern of office worker over 26 days in Seoul, Korea. The relationship between the MicroPEM and the ambient air monitor showed good linearity. Personal exposure and ambient concentrations of PM2.5 were highly correlated with a fixed time-activity pattern compared with PM10. The finding implied a high infiltration rate of PM2.5 and low infiltration rate of PM10. The relationship between personal exposure and ambient concentrations of PM10 and PM2.5 was different for high level episodes. In the Asian dust episode, staying indoors could reduce personal exposure to PM10. However, personal exposure to PM2.5 could not be reduced by staying indoors during the fine dust advisory episode.