Urinary Excretion of 2/3-Monochloropropanediol (2/3-MCPD) and 2,3-Dihydroxypropylmercapturic Acid (DHPMA) after a Single High dose of Fatty Acid Esters of 2/3-MCPD and Glycidol: A Controlled Exposure Study in Humans.

2- and 3-monochloropropanediol (2/3-MCPD) and glycidol are absorbed in the intestine after lipase-catalyzed hydrolysis of their fatty acid esters. In an exposure study with 12 non-smoking participants, the complete urinary excretion of the metabolite 2,3-dihydroxypropylmercapturic acid (DHPMA) and of 2/3-MCPD is measured on four consecutive days before and after consumption of 50 g glycidyl ester-rich palm fat or 12 g 2/3-MCPD ester-rich hazelnut oil. After controlled exposure, urinary excretion rates of 2/3-MCPD per hour strongly increase, followed by a decrease with average half-lives of 5.8 h (2-MCPD) and 3.6 h (3-MCPD). After consumption of hazelnut oil, mean excretion rates are 14.3% (2-MCPD) and 3.7% (3-MCPD) of the study doses. The latter rate is significantly higher (4.6%) after consumption of palm fat, indicating partial conversion (about 5%) of glycidol to 3-MCPD under the acidic conditions in the stomach. The average daily "background" exposure is estimated to be 0.12 and 0.32 µg per kg body weight (BW) for 2-MCPD and 3-MCPD, respectively. The relatively high and constant urinary excretion of DHPMA does not reflect the controlled exposure. Urinary excretion of 2- and 3-MCPD is suitable as biomarker for the external exposure to the respective fatty acid esters.