Harvard T.H. Chan School of Public Health, Boston, MA, USA.
Purdue University, School of Health Sciences, West Lafayette, IN, USA.
J Expo Sci Environ Epidemiol. 2022 May;32(3):427-433. doi: 10.1038/s41370-021-00358-w. Epub 2021 Jul 1.
Toenail metal concentrations can be used as an effective biomarker for exposure to environmental toxicants. Typically toenail clippings are measured ex vivo using inductively coupled plasma mass spectrometry (ICP-MS). X-ray fluorescence (XRF) toenail metal measurements done on intact toenails in vivo could be used as an alternative to alleviate some of the disadvantages of ICP-MS. In this study, we assessed the ability to use XRF to measure toenail metal concentrations in real-time without having to clip the toenails (i.e., in vivo) in two occupational settings for exposure assessment of manganese and mercury.
The portable XRF method used a 3-min in vivo measurement of toenails prior to clipping and was assessed against ICP-MS measurement of toenail clippings taken immediately after the XRF measurement and work history for a group of welders (n = 16) assessed for manganese exposure and nail salon workers (n = 10) assessed for mercury exposure.
We identified that in vivo XRF metal measurements were able to discern exposure to manganese in welders and mercury in nail salon workers. We identified significant positive correlations between ICP-MS of clippings and in vivo XRF measures of both toenail manganese (R = 0.59, p = 0.02) and mercury (R = 0.74, p < 0.001), as well as between in vivo XRF toenail manganese and work history among the welders (R = 0.55, p = 0.03). We identified in vivo XRF detection limits to be 0.5 µg/g for mercury and 2.6 µg/g for manganese. Further work should elucidate differences in the timing of exposure using the in vivo XRF method over toenail clippings and modification of measurement time and x-ray setting to further decrease the detection limit. In vivo portable, XRF measurements can be used to effectively measure toenail Mn and Hg in occupational participants in real-time during study visits and at a fraction of the cost.
指甲金属浓度可用作暴露于环境毒物的有效生物标志物。通常使用电感耦合等离子体质谱法（ICP-MS）对指甲屑进行离体测量。体内活体完整指甲的 X 射线荧光（XRF）指甲金属测量可替代 ICP-MS 以减轻其一些缺点。本研究旨在评估使用 XRF 在无需剪指甲（即体内）的情况下实时测量指甲金属浓度的能力，分别在两个职业暴露评估中用于评估锰和汞：焊工（n=16）和美甲沙龙工人（n=10）。
便携式 XRF 方法在剪指甲前进行 3 分钟的体内测量，然后将其与指甲屑的 ICP-MS 测量值进行比较，指甲屑是在 XRF 测量后立即采集的，并结合工作史进行比较。研究对象为一组评估锰暴露的焊工和一组评估汞暴露的美甲沙龙工人。
我们发现，体内 XRF 金属测量能够区分焊工的锰暴露和美甲沙龙工人的汞暴露。我们发现，指甲屑 ICP-MS 与体内 XRF 对指甲锰（R=0.59，p=0.02）和汞（R=0.74，p<0.001）的测量之间存在显著正相关，以及焊工体内 XRF 指甲锰与工作史之间存在显著正相关（R=0.55，p=0.03）。我们确定体内 XRF 检测下限为汞 0.5μg/g，锰 2.6μg/g。进一步的工作应该阐明使用体内 XRF 方法与指甲屑相比在暴露时间上的差异，并对测量时间和 X 射线设置进行修改，以进一步降低检测下限。体内便携式 XRF 测量可用于在研究访问期间实时有效地测量职业参与者的指甲 Mn 和 Hg，且成本仅为指甲屑的一小部分。
