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Determination of Hippuric Acid and Methylhippuric Acid Isomers in the Urine of Gas Stations Workers

Background: The purpose of this study was to determine the concentration levels of hippuric acid and 2, 3, 4- methyl hippuric acid isomers as biological indicators of exposure to toluene and xylene isomers in the urine of the gas stations workers of Ahvaz, Iran. Methods: The urine sample was taken the first time in January and the second time in June 2018. Eight gas stations were selected in Ahvaz, Khuzestan Province, Iran. The study sample was 24 males; three workers participated in the study from each gas station. Two workers in each gas station served as the exposed group, and one secretary from each gas station was the control group. The participants’ ages ranged from 21 to 49 years. Each participant was requested to fill out a consent form to participate in the study and a questionnaire containing personal information such as age, smoking, weight and height, and work experience. Results: The mean concentration of hippuric acid, 2, 3 and 4- methyl hippuric acid in the investigated urine of the workers were 0.245, 0.017, 0.012, and 0.011 g/g creatinine, respectively. There was no relationship between variable of season and levels of hippuric acid, 2, 3 and 4- methyl hippuric acid in the urine of exposed and control groups. Conclusion: There was no significant difference in the analyzed results of urine samples between control and exposure groups. There was at least one methyl hippuric acid isomer, indicating that all subjects were exposed to xylene, which was lower than the threshold limit value. In conclusion, the variable of season cannot cause a significant change in the metabolites of toluene and xylene isomers. Exposure of workers to toluene and xylene at gas stations is within acceptable limits.