The KXRF bone Pb measurement system was used to measure tibia bone Pb as a metric of each individual’s cumulative lead exposure. The setup was the same as used in previous studies (Nie, 2005 ; Nie et al., 2004 ; Specht et al., 2014 ). The system uses four 16 mm diameter high-purified germanium detectors with 10 mm thickness, four feedback resistance pre-amplifiers, four digital signal processing systems and a computer. A 135 mCi Cd-109 source with 0.8 mm copper filter is used to irradiate tibia bone to produce the Pb K X-rays. Before measurement, the subjects’ legs were cleaned using alcohol and EDTA cotton swabs to remove any Pb contamination. For the KXRF measurement, the subject would sit on a wooden chair. The subject’s leg was immobilized by using two Velcro straps to attach their leg to the leg of the chair at the ankle and just below the knee. The measurement site was mid-tibia with the source at a distance to maintain ~30% dead time during the measurement. The measurement was taken for 30 min while the subject watched a movie. Finally, the spectra were analyzed using an in-house peak-fitting program, which gave results and error for each of the four detectors (Bevington & Robinson, 2003 ; Nie, 2005 ; Somervaille et al., 1989 (link)). This error and result was combined using inverse variance weighting (Todd, 2000 (link)). XRF provides a point estimate of Pb concentration, which can be negative if an individual’s bone Pb is close to zero. It is important to include these negative values, as with their associated uncertainties they are still a point estimate of that individual’s bone Pb.
The whole body effective dose delivered to the subject from this system was estimated to be less than 5 µSv for this population (Nie et al., 2007 ).
The whole body effective dose delivered to the subject from this system was estimated to be less than 5 µSv for this population (Nie et al., 2007 ).
