Background

Potentially toxic elements, such as lead, can bioaccumulate and alter human physiology. Human biomonitoring is an essential tool to evaluate chemical exposures in different biological matrices (blood, urine, saliva, nails, and hair). Of these biological matrices, nails are favorable for their ease of sampling, transport and storage. The aim of this study was to investigate possible correlations between blood lead levels (BLL) and washed and non-washed fingernail lead levels (FLL) in 55 adults living in a lead-contaminated area.

Method

Venous blood and fingernail (thumbs and forefingers) samples were collected. Nails from the left hand were washed with Triton X-100 (0.5 % m/v) and HNO₃ solution, while nails from the right hand were not submitted to the pre-analytical procedures. Samples were analyzed by graphite furnace atomic absorption spectrometry, and pairwise correlations were used to correlate lead concentrations between BLL and FLL; nails from fingers of the same hand and between washed and unwashed fingernails. Principal component analysis was performed and scatter diagrams were plotted to investigate correlations.

Results

A non-significant positive correlation was found between BLL and washed forefinger nails lead (r = 0.219, p = 0.112) and between BLL and thumbnail lead levels (r = 0.182, p = 0.191). Comparison of fingernails from the same hand (thumb and forefinger), showed that lead concentrations of non-washed nails varied widely, even on analyses of transversal fragments from the same nail. Lead levels in non-washed forefinger nails were not correlated with non-washed thumbnails (r = 0.169, p = 0.219). Conversely, washed thumb and forefinger nails were found to be correlated (r = 0.39, p = 0.003). Washed and non-washed nails were also found to be correlated (p < 0.0001).

Conclusion

In conclusion, the results showed that non-washed nails are not a reliable biomarker for lead exposure. Although washing nails before analysis may reduce external contamination, the correlation of lead concentrations between fingers is poor for fingernail lead levels to serve as an internal dose biomarker to lead exposure. In addition, levels in washed nails were not significantly correlated with blood lead levels. Fingernail lead levels seem to serve as an indicator of lead exposure sources in contact with the individual, but not as a reliable biomarker of internal dose.

中文翻译：

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指甲铅水平是铅内剂量的可靠生物标志物吗？

背景

潜在的有毒元素，例如铅，可以生物累积并改变人体生理机能。人体生物监测是评估不同生物基质（血液、尿液、唾液、指甲和头发）中化学物质暴露的重要工具。在这些生物基质中，指甲易于取样、运输和储存。本研究的目的是调查生活在铅污染地区的 55 名成年人的血铅水平 (BLL) 与洗过和未洗过的指甲铅水平 (FLL) 之间可能的相关性。

方法

收集静脉血和手指甲（拇指和食指）样本。左手的指甲用 Triton X-100 (0.5 % m/v) 和 HNO ₃溶液清洗，而右手的指甲不进行预分析程序。通过石墨炉原子吸收光谱法分析样品，并使用成对相关性来关联 BLL 和 FLL 之间的铅浓度；来自同一只手的手指以及洗过和未洗过的指甲之间的指甲。进行主成分分析并绘制散点图以研究相关性。

结果

在 BLL 和洗过的食指指甲铅 ( r  = 0.219, p  = 0.112) 之间以及BLL 和拇指指甲铅水平 ( r  = 0.182, p  = 0.191)之间发现了非显着的正相关。对来自同一只手（拇指和食指）的指甲的比较表明，未洗过的指甲的铅浓度差异很大，即使是对来自同一只指甲的横向碎片的分析也是如此。未洗过的食指指甲中的铅含量与未洗过的拇指指甲无关 ( r  = 0.169, p  = 0.219)。相反，发现洗过的拇指和食指指甲是相关的（r  = 0.39，p = 0.003）。还发现洗过和未洗过的指甲是相关的（p  < 0.0001）。

结论

总之，结果表明未洗过的指甲不是铅暴露的可靠生物标志物。尽管在分析前洗指甲可以减少外部污染，但手指之间铅浓度的相关性很差，因为指甲铅水平作为铅暴露的内部剂量生物标志物。此外，洗过的指甲中的水平与血铅水平没有显着相关性。指甲铅水平似乎可以作为与个人接触的铅暴露源的指标，但不能作为体内剂量的可靠生物标志物。