Assessing benzene exposure is a public health priority due to its deleterious health effects and ubiquitous industrial and environmental sources of exposure. Phenyl mercapturic acid (PhMA) is a commonly used urinary biomarker to assess benzene exposure. However, recent work has identified significant interlaboratory variation in urinary PhMA concentrations related to methodological differences. In this study, we present urinary 6-hydroxy-2,4-cyclohexadienyl mercapturic acid (pre-PhMA), a metabolite that undergoes acid-catalyzed dehydration to form PhMA, as a novel and specific urinary biomarker for assessing benzene exposure. We developed and validated the first quantitative liquid chromatography-tandem mass spectrometry assay for measuring urinary concentrations of pre-PhMA. The pH effect on the method of ruggedness testing determined that pre-PhMA is stable across the normal human urine pH range and that neutral conditions must be maintained throughout quantification for robust and accurate measurement of urinary pre-PhMA concentrations. The method exhibited below 2 ng/mL sensitivity for pre-PhMA, linearity over three orders of magnitude, and precision and accuracy within 10%. Urinary pre-PhMA concentrations were assessed in 369 human urine samples. Smoking individuals exhibited elevated levels of pre-PhMA compared to non-smoking individuals. Furthermore, the relationship between benzene exposure and urinary pre-PhMA levels was explored by examining the correlation of pre-PhMA with 2-cyanoethyl mercapturic acid, a smoke exposure biomarker. The urinary biomarkers exhibited a positive correlation (r = 0.720), indicating that pre-PhMA levels increased with benzene exposure. The results of this study demonstrate that urinary pre-PhMA is a rugged and effective novel biomarker of benzene exposure that can be widely implemented for future biomonitoring studies.

中文翻译：

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评估尿 6-羟基-2,4-环己二烯基硫醇酸作为苯暴露的新型生物标志物。

由于苯对健康的有害影响以及无处不在的工业和环境接触源，评估苯接触情况是公共卫生的首要任务。苯硫醇酸 (PhMA) 是一种常用的尿液生物标志物，用于评估苯暴露。然而，最近的研究发现，与方法学差异相关的尿液 PhMA 浓度存在显着的实验室间差异。在这项研究中，我们提出了尿液中的 6-羟基-2,4-环己二烯基硫醇酸 (pre-PhMA)，这是一种经过酸催化脱水形成 PhMA 的代谢物，作为评估苯暴露的新型特异性尿液生物标志物。我们开发并验证了第一个定量液相色谱-串联质谱测定法，用于测量尿中 pre-PhMA 浓度。pH 对耐用性测试方法的影响决定了 pre-PhMA 在正常人尿 pH 范围内是稳定的，并且在整个定量过程中必须保持中性条件，以便稳健、准确地测量尿液 pre-PhMA 浓度。该方法对 pre-PhMA 的灵敏度低于 2 ng/mL，线性度超过三个数量级，精密度和准确度在 10% 以内。对 369 份人类尿液样本中的尿液 pre-PhMA 浓度进行了评估。与不吸烟个体相比，吸烟个体表现出较高水平的 pre-PhMA。此外，通过检查 pre-PhMA 与 2-氰乙基硫醇酸（烟雾暴露生物标志物）的相关性，探讨了苯暴露与尿液 pre-PhMA 水平之间的关系。尿液生物标志物表现出正相关性（r = 0.720），表明 PhMA 前水平随着苯暴露而增加。本研究的结果表明，尿液 pre-PhMA 是一种坚固且有效的新型苯暴露生物标志物，可广泛应用于未来的生物监测研究。