Benzene exposure is of particular concern because recent research indicating that benzene exposure can result in chronic toxicity, therefore, monitoring for benzene exposure among at-risk workers is recommended. In exposure- and risk-evaluation, the monitoring of benzene by peripheral biomarker has several advantages over technical assessment of exposure. For this purpose, the urine trans, trans muconic acid (ttMA)e level is accepted as a useful monitoring tool for early diagnosis of dangerous exposure. Apart from the industrial workers, there are other occupations with high risk for benzene exposure. In this study, we study another at-risk occupation, the police. Thirty-nine urine samples were obtained from 39 Thai police working close to traffic in an urban area. All 39 samples were analyzed for ttMA level and compared to 10 other controls. The average urine ttMA level for the control and exposed group were < 0.05 mg/gCr and was 0.79 +/- 1.43 mg/gCr, respectively. Significant higher urine ttMA acid level among the police were observed (p <.05). Working in the air pollution in the urban area can be health hazard for the police. Exposure to the benzene from automobile exhaust can be an important occupational problem for these police.