Mercapturic Acids Proper Biological Markers for Occupational Exposure s to Acrylonitrile

1. Mercapturic Acids Proper Biological Markers for Occupational Exposure s to Acrylonitrile Chia-Fang Wu, Kuen-Yuh Wu Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, Taipei, Taiwan Introduction A biological marker is defined as as a xenobiotic chemical or its metabolite or adduct and it could be applied to evaluate the effect and susceptibility of exposure. Mercapturic acid is the endpoint metabolite of a xenobiotic chemical that is detoxified by conjugating with glutathione, and it is used widely nowadays as a biological marker to assess short-term exposure. The risk of the targeting populations could be evaluated by biomonitoring process. In the present study, acrylonitrile(AN), the possible human carcinogen, would be applied as an example, by developing a UPLC-MS/MS method to quantify three major mercapturic acids of acrylonitrile and cotinine (COT) simultaneously (Figure 1), to validate mercapturic acids as proper biological markers for occupational exposure to acrylonitrile. Materials and Methods Urine samples were collected from workers in AN-used factories and stored at -20℃ until use. A Thermo Scientific TSQ Quantum Access UPLC-MS/MS system equipped with a heated electron spray ionization (H-ESI) ion source was applied. Liquid chromatographic separation was performed by a Waters Acquity UPLC column (HSS T3 1.8 μm, 2.1x100 mm) coupled with a pre-column (HSS T3 1.8 μm, 2.1x5 mm) in front of it. The binary system of mobile phase was consisted of 0.1% formic acid in acetonitrile (A) and 0.1% formic acid (B). Results and Discussions Occupational exposure Exposure source Cigarette Exposed group N=79 Non-exposed group N=18 Figure 1. Acrylonitrile metabolism HEMA3.4 min d4-HEMA 3.4 min CEMA 5.9 min d3-CEMA 5.9 min CHEMA 4.4 min COT 1.7 min d3-COT 1.7 min Figure 2. Chromatogram of analytes Conclusions A reliable, accurate and high-sensitive method for simultaneous quantification of major mercapturic acids of AN and cotinine has been developed successfully. The concentration of each analyte did some effect on each other, and there exists a correlation between CEMA and CHEMA for exposed group and CEMA and COTfor non-exposed group. The result implied that direct conjugation with glutathione might be the major metabolized pathway of AN for human. Mercapturic acids are validated as probable biological markers for occupational exposure. This high-throughput method could be applied to future molecular epidemiology studies on the development of metabolite profiles and the quantitative metabonomics of AN in human.