VALIDATION OF K-XRF BONE LEAD MEASUREMENT IN YOUNG-ADULTS

K-X-ray fluorescence (K-XRF) is a useful tool for assessing environmen tal exposure to lead in occupationally exposed individuals and older a dults. This study explores the possibility of using this technique on young adults with low environmental lead exposure Twenty-three college students aged 18-21 years, were recruited for 2 hr of bone lead measu rement. Bone lead measurements were taken from the mid-shaft tibia for periods of 30 or 60 min. In the analysis, 30-min measurements were co mbined so that each subject had the equivalent of two 60-min measureme nts. The average concentration of two bone lead measurements in this p opulation ranged from 1.5 to 8.2 mu g Pb/g bone mineral, with a mean o f 3.0 mu g Pb/g bone mineral. In a one sample t-test, this mean was si gnificantly, different from 0 (p<0.0001). A linear trends with age was detected despite the small age range of our population. By doubling t he sampling time, the reported measurement uncertainty decreased by a factor of 1.5, resulting in uncertainty estimates below the mean bone lead estimates. Power calculations using the observed variance estimat es suggest that with 80% power, differences in bone lead concentration of 2-3 mu g Pb/g bone mineral can be identified in groups of 100 or s maller. Due to the large within-person variation in young adults, K-XR F may not yet be a useful diagnostic tool for individual subjects, but it may be of great use to environmental scientists trying to characte rize long-term lead exposure and dose in the general population or spe cific subpopulations.