Abstract
Di(isononyl)cyclohexane-1,2-dicarboxylate (DINCH) is used as an alternative for some phthalate plasticizers. In rats, DINCH mostly eliminates in feces as cyclohexane-1,2-dicarboxylic acid (CHDA), mono isononyl ester (MINCH) or in urine as CHDA. However, CHDA is not a specific biomarker of DINCH and measuring MINCH in feces is impractical. To identify additional potential biomarkers, we administered DINCH (500 mg/kg body weight) in a single subcutaneous (SC) or oral dose to four adult female Sprague–Dawley rats. We collected 24-h urine samples before dosing (to be used as controls) and 24-h and 48-h after dosing, and serum at necropsy after 48 h. We positively identified and accurately quantified CHDA and cyclohexane-1,4-dicarboxylic acid, mono hydroxyisononyl ester (MHNCH) using authentic standards. Moreover, we tentatively identified MINCH and 12 oxidative metabolites, including 4 cyclohexane ring oxidation products, based on their mass spectrometric-fragmentation patterns. CHDA and MHNCH levels were higher in the urine collected 24 h after oral than SC administration. By contrast, 48-h after dosing, CHDA urinary levels were similar regardless of the exposure route. We detected all but two of the urine metabolites also in serum. Levels of CHDA and MHNCH in serum were lower than in the two post-dose urine collections. Our results suggest that several urinary oxidative metabolites, specifically CHDA, mono oxoisononyl ester and MHNCH may be used as specific biomarkers of DINCH exposure in humans.
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Acknowledgements
We thank Dr. Raymond David (BASF) for providing DINCH.
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The animal research described in this article has been reviewed by the National Health Environmental Effects Research Laboratory, US Environmental Protection Agency and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
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Silva, M., Furr, J., Preau, J. et al. Identification of potential biomarkers of exposure to di(isononyl)cyclohexane-1,2-dicarboxylate (DINCH), an alternative for phthalate plasticizers. J Expo Sci Environ Epidemiol 22, 204–211 (2012). https://doi.org/10.1038/jes.2011.43
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DOI: https://doi.org/10.1038/jes.2011.43