In this study, we have been able to observe statistically significant differences in levels of both urinary metabolites in samples collected in rural school children and Bangkok city school children despite the relatively low levels of exposure. Additionally, t,t-muconic acid levels in urine samples collected in the afternoon, and 1- OHP levels in samples collected the following morning, did show a statistically significant correlation with per- sonal exposures to benzene and PAHs, respectively. This would seem to indicate that these are useful biomarkers of exposure, particularly since they are alsonon-invasive. However, only DNA adducts are generally accepted as being predictive of health effects, such as cancer (Vineis and Perera, 2000; Rundle et al., 2000).