biomarkers of early biological effects, in school children are summarized in Table 4. DNA strand breaks, as measured by olive tail moment, are significantly higher in Bangkok school children than in Chonburi school chil- dren (P < 0.001). At the same time, DNA repair capacity, as measured by the levels ofradiation-induced dicentrics and deletions per metaphase cell, is significantly lower in Bangkok school children when compared with Chonburi school children (P < 0.001).