In vivo Quantification of Bone Lead and Strontium using Portable X-ray Fluorescence (XRF)

Abstract

BACKGROUND AND AIM: Exposure to lead (Pb) or strontium (Sr) is of concern due to potential neurotoxicity or impaired bone health, respectively. Human bone is reliable biomarker for cumulative Pb and Sr exposures and for studying associated health outcomes. However, the applicability of standard K-shell x-ray fluorescence (KXRF) bone Pb measurement technology is significantly limited by its lack of portability, long measurement times, and licensing - restricting its use in large-scale population studies. In this study, we measured Pb and Sr in two populations using portable x-ray fluorescence (XRF), compare bone Pb measurements from a portable XRF device and a KXRF device, and assess differences in bone Sr level across sex, age and ethnicity. METHODS: We measured bone Pb and Sr concentrations in mid-tibia bone using portable XRF in 76 Americans, age 38 – 95 years, living in Indiana, and bone Sr concentrations in 29 Chinese, age 53 – 82 years, living in Shanghai. RESULTS:The detection limits for 3-minute portable XRF measurements for in vivo bone Pb and Sr ranged from 4.0 to 12.6 ug/g dry bone (ppm) and 2.0 to 5.2 ppm, respectively, with overlying soft tissue (ST) thickness ranging from 2 to 6 mm. Bone Pb measurements via KXRF and portable XRF were highly correlated: R = 0.73 (95% CI, 0.28 to 0.70) among participants with ST thickness 6 mm (72% of the measured population). Furthermore, the mean bone Sr concentration for American participants was 66.1 ppm (95%CI: 56.5 ppm, 75.6 ppm) and for Chinese was 74.7 ppm (95%CI: 55.6 ppm, 93.8 ppm). Interestingly, the bone Sr in Chinese female participants decreased with age, while the bone Sr in American female participants increased with age. CONCLUSIONS:We conclude that portable XRF is a valuable technology to study health outcomes related to Pb and Sr exposures. KEYWORDS: Heavy Metals, Exposure Assessment, X-ray Fluorescence, Lead (Pb), Strontium (Sr)