| Benzene is an important industrial chemical and, due to its occurrence in mineral oil and its formation in many combustion processes, a widespread occupational and environmental pollutant. Since benzene is hematoxic and has been classified as a human carcinogen, monitoring and control of benzene exposure is of importance. Most of the urinary metabolites of benzene and unmetabolized benzene in urine have been extensively investigated as biological markers of exposure to benzene. The biomarkers of recent exposure were urinary metabolites (measuring responses up to hours after exposure), Including phenol, catechol, hydroquinone, benzenetriol, S-phenylmercapturic acid , trans,trans-Muconic Acid and adducts of blood proteins(days to weeks after exposure) which including benzene axide and benzoquinone adducts of albumin. The biomarker of longer-term exposure were chromosomal changes,integrating exposure over months to years. S-PMA and ttMA in urine might be the most useful markers of recent benzene exposure. Both markers had low background levels in unexposed workers and increased levels in exposed workers. S-PMA was found to be the most useful biomarker for recent exposure to benzene because of the extent of the change in its levels, its sensitivity in correlating with low occupational benzene exposures, and its specificity for benzene exposure. But the detection of S-PMA requires high standards of instrument, while the method of detection of trans,trans-muconic acid is likely to be wide-spread accepted by those poor-equipped departments. Other urinary metabolites were less sensitive to change in benzene exposure and had higher background levels than S-PMA and ttMA. Therefore, these markers were less suitable as biomarker for detecting dose-dependent low level exposure of benzene.Considering the instrumental conditions of our laboratary and comparing series biomarkers of benzene, We choose trans,trans-muconic acid as subject of our study. To establish the biological limit values for occupational exposure to benzene in China and the method of the determination of urinary trans,trans-muconic acid by high performance liquid chromatography . Study participants were recruited from 56 benzene-exposed workers and 24 unexposed workers. The personal exposure to benzene was measured by the sampling of worker's breathing zone on sorbent tubes with active charcoal followed by elution with carbon disulphide and capillary gas chromatographic determination. The individual internal exposure was assessed by determination of ttMA in urine by HPLC method. The urine samples were collected at the beginning and end of the work shift and were acidified by 2mol/L of hydrochloric acid, addition of vanillic acid as an internal standard and pretreated by liquid–liquid extraction using diethyl ether. An ODS C18 column was used, glacial acetic acid-tetrahydrofuran-methanol-water (1:2:10:87) as mobile phase, flowing at 0.9mL/min, UV detection at 264 nm and column temperature maintained at 25℃for ttMA separation. The linearity range of calibration curve was 0.1 mg/L-10.00mg/L and the limit of detection was 0.10mg/L, the average recovery rate ranged from 95.1% to 100.5%. The intra-day and inter-day precisions (RSD) for the analysis were 4.4%-7.5% and 6.2%-8.8%, respectively. The analytic findings showed the benzene exposure level ranged from 0.332～146mg/m~3 with...
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