Experimental study on the metabolism of dimethylethylamine in man

Dimethylethylamine (DMEA) is an aliphatic tertiary amine, which is used as a catalyst in the mould core manufacturing. During 8 h, four healthy volunteers were exposed to four different DMEA air concentrations (10, 20, 40 and 50 mg/m3; 20 mg/m3, two subjects only). DMEA was biotransformed into dimethylethylamine N-oxide (DMEAO). On average, DMEAO, accounted for 90% of the combined amount of DMEA and DMEAO excreted into the urine. The half-lives of DMEA and DMEAO in plasma were 1.3 and 3.0 h, respectively. The urinary excretion of DMEA and DMEAO followed a two-phase pattern. The half-lives in the first phase were 1.5 h for DMEA and 2.5 h for DMEAO. In the second phase, which started about 9 h after the end of exposure, half-lives of 7 h for DMEA and 8 h for DMEAO were recorded. The combined concentration of DMEA and DMEAO, in both plasma and urine, showed an excellent correlation with the air concentration of DMEA. Thus, both urinary excretion and plasma concentration can be used for biological monitoring of exposure to DMEA. An 8-h exposure to 10 mg DMEA/m3 corresponds to a postexposure plasma concentration and 2-h postexposure urinary excretion of 4.9 mumol/l and 75 mmol/mol creatinine, respectively.