The effect of measurement location on tibia lead XRF measurement results and uncertainty

The aims of this study were to determine whether the location on the tibia measured by 109Cd-based K-shell x-ray fluorescence (XRF) affected the measurement result and its uncertainty, and whether higher tibia lead levels at the extremities of the tibia and/or inhomogeneity in the distribution of lead in the tibia could be inferred therefrom. Replicate XRF measurements were performed at multiple locations on ten adult cadaver intact legs and on nine bare tibiae dissected from them. Mean lead levels in the bare tibiae ranged from 16 to 48 microg Pb per g of bone mineral. Bare tibia measurements showed that both the XRF result and its uncertainty increased towards the proximal and distal ends of the tibia. The XRF result decreased away from the medial-lateral mid-point of the tibia, but XRF uncertainty was not significantly affected. Intact leg measurements showed no effect of proximal distal location on XRF result but did show an effect on XRF uncertainty. We conclude that the XRF method used can determine the differences in bone lead level resulting from the more trabecular composition at the ends of the tibia, and we present limited evidence for localized regions of low tibia lead level.