SEASONAL EXPOSURE TO NO2 AND RESPIRATORY SYMPTOMS IN PRESCHOOL-CHILDREN

One hundred seventy-two preschool children, aged three to six years, w ho attended municipal day-care centers in central and suburban areas o f Helsinki, were followed up for seven weeks during the winter season and for eight weeks during the spring season in 1991. For each child, the weekly average NO2 exposure was estimated using passive samplers a ttached to the outer garments of the children during their everyday ac tivities. Respiratory symptoms were recorded in daily diaries by the p arents. The median of personally measured seasonal NO2 exposures was 2 1 mu g/m(3) (range 11-45.8 mu g/m(3)). The seasonal median NO2 exposur e was significantly larger (p < 0.001) in the central area (27.4 mu g/ m(3)) than in the suburban area (18.2 mu g/m(3)), reflecting a differe nce in exposure caused by automobile traffic. There also were signific antly (p < 0.001) more days with stuffed nose (26% vs. 20%) and cough (18% vs. 15%) in the central area than in the suburban area. At the in dividual level, there was a nonsignificant positive correlation betwee n personal NO2 exposure and cough during the spring season. Thus the a real difference in these symptoms was partly, but not completely, due to the difference in exposure to NO2.