PERSONAL NO2 EXPOSURES OF PRESCHOOL-CHILDREN IN HELSINKI

Weekly personal NO2 exposures of 246 children aged 3-6 years were meas ured with Palmes tubes during 13 weeks in winter and spring in 1991. M easurements were made in eight day-care centers in the downtown and su burban areas of Helsinki, Finland. At the same time, inside and outsid e NO2 concentrations of the day-care centers and the ambient air fixed site measurements were conducted. Palmes tubes were found to be appli cable for NO2 exposure measurements of preschool children, but rather high sample losses could be expected. The geometric mean of personal N O2 exposure levels of 13-week period was 26.5 mu g/m(3) in the downtow n and 17.5 mu g/m(3) in the suburban area. Gas stove and smoking at ho me increased significantly personal exposure to NO2. The weekly popula tion NO2 exposures correlated rather poorly with the fixed site ambien t air NO2 levels (R-2 = 0.37), but much better with the NO2 levels ins ide and outside the day-care centers (R-2 = 0.88 and 0.86). In the sub urban and downtown groups the between children variations in the NO2 e xposures were only 14% and 28% of the total variations, which were dom inated by the within child variation. Stationary measurements at the a mbient air fixed sites and inside and outside the day-care centers exp lained the variation in personal exposures of the children well during the spring, but not during the winter. A regression model, where data from outside day-care center measurements, fixed ambient air monitors , residential area and home characteristics (i.e., gas stove, smoking inside at home, type of dwelling) were included, explained 32% of the personal NO2 exposure variation in winter and 67% in spring. In the ab sence of personal exposure measurements, both stationary measurements and questionnaire information are useful in estimating variations in p ersonal exposures.