Cortical porosity and the accuracy of 109Cd K XRF bone lead measurements in pre-menopausal women

• 109 Cd K XRF bone Pb measurement accuracy is not affected by changes in tibia cortical porosity. • Monte Carlo modelling shows that in vivo heterogeneous distributions of bone Pb do not perturb XRF measurement accuracy. • Large tissue overlay thickness results in inaccurate 109 Cd K XRF tibia Pb measurements. • A non-linear endogenous exposure relationship between blood and bone Pb levels in young women has been observed Studies were performed to test whether tibia cortical porosity could create measurement artifacts in 109 Cd K XRF bone lead (Pb) measurements using Pb-doped plaster of Paris phantoms with a three-dimensional (3D) printed PLA lattice. Phantoms were modelled in MCNP to test the effect of cortical porosity; heterogeneous distributions of Pb; and extremely large tissue overlay thickness on bone Pb measurement accuracy. Modelling showed that cortical porosity of the tibia did not affect the measurement accuracy; measurements were inaccurate in phantoms with extreme heterogeneous distributions of Pb. However, it is only at unrealistic levels of heterogeneity (that are unlikely to be encountered in vivo ) that the measurement becomes inaccurate; and large tissue overlay thicknesses resulted in inaccurate 109 Cd K XRF bone Pb measurements. When blood and 109 Cd K XRF bone Pb data of morbidly obese women were excluded, age related changes in endogenous exposure to Pb were observed in pre-menopausal women.