Repeatability of Tibia Lead Measurement by X-Ray Fluorescence in a Battery-Making Workforce

The purpose of this study was to remeasure in vivo tibia lead levels in a lead–acid battery manufacturing workforce measured in a previous survey and believed to be unrealistically high. Tibia lead levels were measured by K-shell X-ray fluorescence (XRF) spectroscopy in a stratified random sample (n=40) of the original study group (n=381). The repeat survey showed much lower tibia lead levels (median=54.3 μg lead/g bone mineral, compared to 217.9 μg lead/g bone mineral, n=40). Tibia lead levels were significantly correlated with duration of occupational exposure, zinc protoporphyrin levels, and cumulative blood lead index, but not with current blood lead levels. Thirty-eight of the 40 subjects underwent two consecutive tibia lead measurements to assess the test–retest repeatability of the XRF tibia lead measurement technique. The intraclass correlation coefficient between repeated measurements was 0.926 (P=0.0001). Three measurement pairs differed by more than 20 μg/g. There was no fixed or proportional bias between the two sets of measurements. We conclude that the technique offers a highly repeatable measurement of tibia bone lead. However, care needs to be taken to avoid contamination when performing measurements on active lead workers.