Hepatic microsomal enzyme function in technicians and anesthesiologists exposed to halothane and nitrous oxide

It is controversial whether daily occupational exposure to halothane stimulates (induces) the hepatic microsomal enzyme function in man. We investigated two groups of persons with different degrees of exposure to halothane: Six technicians who for years had been employed with repair and control of anesthesiologic equipment resulting in exposure to about 7 ppm of halothane and 50 ppm of nitrous oxide, and seven anesthesiologists exposed during months to about 2 ppm of halothane and 75 ppm of nitrous oxide. The clearance of antipyrine was determined from saliva concentrations before and 4 wk after discontinuation of exposure. Matched control persons were investigated simultaneously. No significant differences were found between the half-life, apparent volume of distribution, or clearance of antipyrine either within the groups or between the groups. If the antipyrine data from both exposure groups are compared to those of the control groups, the data exclude (95% confidence limit) that antipyrine metabolism increased by more than 3% during exposure to waste anesthetics. This indicates that occupational exposure to halothane in concentrations above the proposed maximal time weighted average concentration of 2 ppm does not change the microsomal activity.