Abstract

Ten male volunteers were exposed to ethylene glycol monoethyl ether acetate (EGEE-Ac) under various conditions of exposure and physical workload. As exposure proceeded, retention, atmospheric clearance, and uptake rate declined slowly to reach steady state levels after three to four hours. Retention increased as a consequence of higher exposure concentrations and of physical workload performed during exposure. Uptake rate was higher as exposure concentration or pulmonary ventilation rate, or both, increased. Subject related factors such as pulmonary ventilation, cardiac output, height, and body fat content also determined individual uptake. During exposure, partial respiratory elimination of EGEE was observed. This finding confirms the hypothesis that EGEE-Ac is first converted to EGEE by (plasma) esterases. The amount of EGEE eliminated at steady state levels correlated more with uptake rate of EGEE-Ac than with exposure concentration. Respiratory elimination of unmetabolised EGEE-Ac accounted for less than or equal to 0.5% of total body uptake. The elimination curves were biexponential indicating that at least two pharmacological compartments are involved. Postexposure breath concentrations were higher as total body uptake increased. Several observations may indicate that the hydrolysis of the ester moiety of EGEE-Ac is hindered by the presence of the natural esterase substrates. With increasing plasma concentrations, however, EGEE-Ac competed more favourably for the available esterase.