Hoet Perrine, De Smedt Erika, Ferrari Massimo, Imbriani Marcello, Maestri Luciano, Negri Sara, De Wilde Peter, Lison Dominique, Haufroid Vincent
Industrial Toxicology and Occupational Medicine Unit, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium.
Int Arch Occup Environ Health. 2009 Aug;82(8):985-95. doi: 10.1007/s00420-008-0381-6. Epub 2008 Nov 14.
trans,trans-Muconic acid (t,t-MA) is generally considered as a useful biomarker of exposure to benzene. However, because of its lack of specificity, concerns about its value at low level of exposure have recently been raised. The aim of this study was (a) to compare t,t-MA, S-phenylmercapturic acid (SPMA) and benzene (B-U) as urinary biomarkers of exposure to low levels of benzene in petrochemical workers and, (b) to evaluate the influence of sorbic acid (SA) and genetic polymorphisms of biotransformation enzymes on the excretion of these biomarkers.
A total of 110 workers (including 24 smokers; 2-10 cigarettes/day) accepted to take part in the study. To assess external exposure to benzene, air samples were collected during the whole working period by a passive sampling device attached close to the breathing zone of 98 workers. Benzene was measured in blood (B-B) samples taken at the end of the shift, and was considered as the reference marker of internal dose. Urine was collected at the end of the shift for the determination of B-U, SPMA, t,t-MA, SA and creatinine (cr). B-U and B-B were determined by head-space/GC-MS, SPMA and SA by LC-MS, t,t-MA by HPLC-UV.
Most (89%) personal measurements of airborne benzene were below the limit of detection (0.1 ppm); B-B ranged from <0.10 to 13.58 mug/l (median 0.405 microg/l). The median (range) concentrations of the urinary biomarkers were as follows: B-U 0.27 microg/l (<0.10-5.35), t,t-MA 0.060 mg/l (<0.02-0.92), SPMA 1.40 microg/l (0.20-14.70). Urinary SA concentrations ranged between <3 and 2,211 microg/l (median 28.00). Benzene concentration in blood and in urine as well as SPMA, but not t,t-MA, were significantly higher in smokers than in non-smokers. The best correlation between B-B and urinary biomarkers of exposure were obtained with benzene in urine (microg/l r = 0.514, P < 0.001; microg/g cr r = 0.478, P < 0.001) and SPMA (microg/l r = 0.495, P < 0.001; microg/g cr r = 0.426, P < 0.001) followed by t,t-MA (mg/l r = 0.363, P < 0.001; mg/g cr r = 0.300, P = 0.002). SA and t,t-MA were highly correlated (r = 0.618, P < 0.001; corrected for cr r = 0.637). Multiple linear regression showed that the variation of t,t-MA was mostly explained by SA concentration in urine (30% of the explained variance) and by B-B (12%). Variations of SPMA and B-U were explained for 18 and 29%, respectively, by B-B. About 30% of the variance of B-U and SPMA were explained by B-B and smoking status. Genetic polymorphisms for biotransformation enzymes (CYP2E1, EPHX1, GSTM1, GSTT1, GSTP1) did not significantly influence the urinary concentration of any of the three urinary biomarkers at this low level of exposure.
At low levels of benzene exposure (<0.1 ppm), (1) t,t-MA is definitely not a reliable biomarker of benzene exposure because of the clear influence of SA originating from food, (2) SPMA and B-U reflect the internal dose with almost similar accuracies, (3) genetically based inter-individual variability in urinary excretion of biomarkers seems negligible. It remains to assess which biomarker is the best predictor of health effects.
反式，反式-粘康酸（t,t-MA）通常被认为是苯暴露的一种有用生物标志物。然而，由于其缺乏特异性，最近人们对其在低暴露水平下的价值提出了担忧。本研究的目的是：（a）比较t,t-MA、S-苯基巯基尿酸（SPMA）和苯（B-U）作为石化工人低水平苯暴露的尿生物标志物；（b）评估山梨酸（SA）和生物转化酶基因多态性对这些生物标志物排泄的影响。
共有110名工人（包括24名吸烟者，每天吸烟2 - 10支）参与了本研究。为评估苯的外部暴露，通过连接在98名工人呼吸区附近的被动采样装置在整个工作期间采集空气样本。在轮班结束时采集血液（B-B）样本测量苯，并将其视为内部剂量的参考标志物。在轮班结束时收集尿液用于测定B-U、SPMA、t,t-MA、SA和肌酐（cr）。B-U和B-B通过顶空/气相色谱-质谱法测定，SPMA和SA通过液相色谱-质谱法测定，t,t-MA通过高效液相色谱-紫外法测定。
大多数（89%）空气中苯的个人测量值低于检测限（0.1 ppm）；B-B范围为<0.10至13.58 μg/l（中位数0.405 μg/l）。尿生物标志物的中位数（范围）浓度如下：B-U 0.27 μg/l（<0.10 - 5.35），t,t-MA 0.060 mg/l（<0.02 - 0.92），SPMA 1.40 μg/l（0.20 - 14.70）。尿SA浓度范围在<3至2211 μg/l之间（中位数28.00）。吸烟者血液和尿液中的苯浓度以及SPMA，但不包括t,t-MA，显著高于非吸烟者。暴露的尿生物标志物与B-B之间的最佳相关性在尿苯（μg/l r = 0.514，P < 0.001；μg/g cr r = 0.478，P < 0.001）和SPMA（μg/l r = 0.495，P < 0.001；μg/g cr r = 0.426，P < 0.001）中得到，其次是t,t-MA（mg/l r = 0.363，P < 0.001；mg/g cr r = 0.300，P = 0.002）。SA和t,t-MA高度相关（r = 0.618，P < 0.001；校正cr后r = 0.637）。多元线性回归表明，t,t-MA的变化主要由尿SA浓度（解释方差的30%）和B-B（12%）解释。SPMA和B-U变化分别由B-B解释18%和29%。B-U和SPMA约30%的方差由B-B和吸烟状态解释。生物转化酶（CYP2E1、EPHX1、GSTM1、GSTT1、GSTP1）的基因多态性在这种低暴露水平下对三种尿生物标志物的尿浓度没有显著影响。
在低水平苯暴露（<0.1 ppm）时，（1）由于来自食物的SA的明显影响，t,t-MA绝对不是苯暴露的可靠生物标志物；（2）SPMA和B-U以几乎相似的准确度反映内部剂量；（3）基于基因的生物标志物尿排泄个体间变异性似乎可以忽略不计。仍有待评估哪种生物标志物是健康影响的最佳预测指标。
