Human inhalation exposure to ethylene glycol

Two male volunteers (A and B) inhaled 1.43 and 1.34 mmol, respectively, of vaporous ¹³C-labeled ethylene glycol (¹³C₂-EG) over 4 h. In plasma, ¹³C₂-EG and its metabolite ¹³C₂-glycolic acid (¹³C₂-GA) were determined together with the natural burden from background GA using a gas chromatograph equipped with a mass selective detector. Maximum plasma concentrations of ¹³C₂-EG were 11.0 and 15.8 μmol/l, and of ¹³C₂-GA were 0.9 and 1.8 μmol/l, for volunteers A and B, respectively. Corresponding plasma half-lives were 2.1 and 2.6 h for ¹³C₂-EG, and 2.9 and 2.6 h for ¹³C ₂-GA. Background GA concentrations were 25.8 and 28.3 μmol/l plasma. Unlabeled background EG, GA and oxalic acid (OA) were detected in urine in which the corresponding ¹³C-labeled compounds were also quantified. Within 28 h after the start of the exposures, 6.4% and 9.3% ¹³C₂-EG, 0.70% and 0.92% ¹³C₂-GA, as well as 0.08% and 0.28% ¹³C₂-OA of the inhaled amounts of ¹³C₂-EG, were excreted in urine by volunteers A and B, respectively. The amounts of ¹³C₂-GA represented 3.7% and 14.2% of background urinary GA excreted over 24 h (274 and 88 μmol). The amounts of ¹³C₂-OA were 0.5% and 2.1% of background urinary OA excreted over 24 h (215 and 177 μmol). From the findings obtained in plasma and urine and from a toxicokinetic analysis of these data, it is highly unlikely that workplace EG exposure according to the German exposure limit (MAK-value 10 ppm EG, 8 h) could lead to adverse effects from the metabolically formed GA and OA.