Human exposure to the plasticizer diisononyl-cyclohexane-1,2-dicarboxylate (DINCH) in the United States

Abstract

Background: Since 2002, diisononyl-cyclohexane-1,2-dicarboxylate (DINCH) is being used as a plasticizer to replace phthalates such as di(2-ethylhexyl)phthalate (DEHP) and di-isononyl phthalate (DINP). Aims: To evaluate exposure to DINCH, DEHP and DINP by using the urinary concentrations of several of their metabolites. Methods: We determined the urinary concentrations of metabolites of DINCH, DEHP and DINP by on-line solid-phase extraction–isotope dilution-high performance liquid chromatography–tandem mass spectrometry in convenience samples of U.S. adults collected between 2000 and 2012. Results: We did not detect monocarboxyisooctyl-cyclohexane-1,2-dicarboxylate (MCOCH), mono(oxoisononyl)cyclohexane-1,2-dicarboxylate (MONCH), and mono(hydroxyisononyl) cyclohexane-1,2-dicarboxylate (MHNCH), three DINCH metabolites, in urine samples collected in 2000 and 2001. Only one of the samples collected in 2007 had measureable concentrations of DINCH metabolites. The detection rate for the three DINCH metabolites increased from 2007 to 2012. The urinary concentrations of MHNCH, MONCH and MCOCH were lower than those of the DEHP and DINP metabolites. We also observed an upward trend in urinary concentrations of the DINP metabolites, but a downward trend in the concentrations of the DEHP metabolites. Conclusions: Exposure to DINCH and to DINP might be increasing in the U.S. general population while exposure to DEHP appears to be decreasing likely as a result of changes in formulation of products, public awareness, and regulations of plasticizers. Because the use of alternatives to phthalate plasticizers might be on the rise, our findings also stress the importance of understanding exposure to these substitutes to evaluate their potential impact on health.