Limited capacity of humans to metabolize tetrachloroethylene

Abstract

Personal monitoring of exposure to tetrachloroethylene (TETRA) with carbon felt dosimeters and analyses of urine for total trichloro-compounds (TTC) were carried out in two groups of workers (36 males and 25 females), one group (20 males and 19 females) in dry-cleaning workshops and the other (16 males and 6 females) engaged in the removal of glue from silk cloth. Comparison of the urinary TTC levels with TETRA in the environment revealed that, while the metabolite levels increased essentially linear to TETRA concentrations up to 100 ppm, leveling off was apparent in the metabolite excretion when the exposure to TETRA was more intense (e.g. more than 100 ppm), indicating that the capacity of humans to metabolize TETRA is rather limited, as previously discussed. From the set of the data thus obtained, screening levels of 30 and 61 mg TTC (as TCA)/l urine as the lower 95% confidence limits for a group mean were calculated for the biological monitoring, by means of urinalysis, of exposure to TETRA at 50 and 100 ppm (TWA), respectively. A tentative calculation with additional exhaled-air analyses indicated that, at the end of an 8-h shift with exposure to TETRA at 50 ppm (TWA), 38% of the TETRA absorbed through the lungs would be exhaled unchanged and less than 2% would be metabolized to be excreted into the urine, while the rest would remain in the body to be eliminated later.

Dose‐excretion relationship in tetrachloroethylene‐exposed workers and the effect of tetrachloroethylene co‐exposure on trichloroethylene metabolism

“…Biological monitoring by means of urinalysis for metabolites has been applied in occupational health practice as a means to assess the exposure of workers to industrial chemicals including TETRA and TRI [Alessio et al, 1983[Alessio et al, , 1986ACGIH, 1988; Deutche Forschungsgemeinschaft, 1988]. Thus, it was learned that metabolism of TETRA in humans is rather readily saturated when exposure is intense [e.g., at 200 ppm and above for 8 hours a day; Ohtsuki et al, 1983] as expected from its chemical stability , although the urinary metabolite levels will hold linearity under less intense exposures, e.g., less than 100 ppm [Ohtsuki et al, 1983]. Taking advantage of this approach of biological monitoring, the balance between the exposure of workers to TETRA and the excretion of metabolites in urine was exam ined in the present study in a group of Chinese dry-cleaning workers.…”

Urinary Excretion of Tetrachloroethylene (Perchloroethylene) in Experimental and Occupational Exposure

“…4 In the postexposure period, 80-95% of tetrachloroethylene is excreted through the lung 17 ; small amounts are excreted in urine as trichloroacetic acid and trichloroethanol. 18 A percentage of absorbed tetrachloroethylene is eliminated as such via the kidneys. 19 This small amount of solvent dissolved in urine collected in the bladder should reach a pressure equilibrium with alveolar air and arterial blood (alveolar-arterial-urinary steady state) .…”

Uncertainties in Pharmacokinetic Modeling for Perchloroethylene. I. Comparison of Model Structure, Parameters, and Predictions for Low‐Dose Metabolism Rates for Models Derived by Different Authors

“…( *~) data make predictions of human metabolite production within a factor of two; and the two models each calibrated with the Ohtsuki et a1. (27) data and the Monster(25)/ Fernandez(I5) data make predictions that are practically identical. (The Droz model, although based on the Monster data, does not actually reproduce it.)…”