National Exposure Research Laboratory, U.S. Environmental Protection Agency, Las Vegas, NV, USA.
Environ Health. 2012 Oct 31;11:81. doi: 10.1186/1476-069X-11-81.
Toenail-Hg levels are being used as a marker of methylmercury (MeHg) exposure in efforts to associate exposure with effects such as cardiovascular disease. There is a need to correlate this marker with more established biomarkers that presently underlie existing dose-response relationships in order to compare these relationships across studies.
As part of the Arsenic Mercury Intake Biometric Study, toenail clippings were collected at three time points over a period of one year amongst females from within the population of Japanese living near Puget Sound in Washington State (US). Variability in temporal intra-individual toenail-Hg levels was examined and chronologically matched hair and toenail samples were compared to more accurately define the toxicokinetic variability of Hg levels observed between the two compartments.
Mean toenail-Hg values (n=43) for the 1st, 2nd and 3rd visits were 0.60, 0.60 and 0.56 ng/mg. Correlations were as follows: r=0.92 between 1st and 2nd clinic visits, r=0.75 between 1st and 3rd visits and r=0.87 between 2nd and 3rd visits. With few exceptions, toenail-Hg values from any visit were within 50-150% of the individual's mean toenail-Hg level. Nearly all participants had less than a two-fold change in toenail-Hg levels across the study period. A regression model of the relationship between toenail-Hg and hair-Hg (n = 41) levels representing the same time period of exposure, gave a slope (Hg ng/mg) of 2.79 for hair relative to toenail (r=0.954).
A chronologically matched hair-Hg to toenail-Hg ratio has been identified within a population that consumes fish regularly and in quantity. Intra-individual variation in toenail-Hg levels was less than two-fold and may represent dietary-based fluctuations in body burden for individuals consuming various fish species with different contaminant levels. The chronologically matched ratio will be useful for relating MeHg exposure and dose-response derived from toenail-Hg measurements to those derived from hair-Hg measurements in other studies, and may be useful in future investigations as an indicator of stable MeHg body burden within a population.
目前，人们正在使用趾甲汞水平作为甲基汞（MeHg）暴露的标志物，以将暴露与心血管疾病等效应联系起来。为了将这些关系与现有的剂量-反应关系所依据的更成熟的生物标志物进行关联，有必要对该标志物进行相关分析。
作为砷汞摄入生物计量研究的一部分，在华盛顿州普吉特湾附近的日本人群中，女性在一年的三个时间点采集趾甲样本。研究考察了个体内时间上的趾甲汞水平的变异性，并对时间上匹配的头发和趾甲样本进行了比较，以更准确地确定在两个隔室之间观察到的汞水平的毒代动力学变异性。
第 1、2 和 3 次就诊的平均趾甲汞值（n=43）分别为 0.60、0.60 和 0.56ng/mg。相关性如下：第 1 次和第 2 次就诊时 r=0.92，第 1 次和第 3 次就诊时 r=0.75，第 2 次和第 3 次就诊时 r=0.87。除了少数例外，任何就诊时的趾甲汞值都在个体平均趾甲汞值的 50-150%范围内。在整个研究期间，几乎所有参与者的趾甲汞水平变化都不到两倍。在代表同一暴露时间段的 41 例头发-汞和趾甲-汞水平的回归模型中，头发相对于趾甲的斜率（Hg ng/mg）为 2.79（r=0.954）。
在一个经常大量食用鱼类的人群中，已经确定了一个时间上匹配的头发-汞与趾甲-汞比值。个体内的趾甲汞水平变化小于两倍，可能代表了个体摄入不同污染物水平的各种鱼类时体内负荷的饮食波动。时间上匹配的比值将有助于将源自趾甲汞测量的 MeHg 暴露和剂量-反应与源自头发-汞测量的暴露和剂量-反应进行关联，并且在未来的研究中可能作为人群中稳定的 MeHg 体负荷的指标有用。
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