and PER OVRUM, M.Sc.! ASTRAND, r., ENGSTROM, J. and OVRUM, P. Exposure to xylene and ethylbenzene: 1. Uptake, distribution and elimination in man. Scand. j. work environ. & health 4 (1978) 185-194. Industrial xylene is a mixture of xylene and ethylbenzene. Twelve male subjects were exposed to industrial xylene in inspired air, six subjects in series I to 870 mg/m S at rest (30 min) and light exercise on a bicycle ergometer (90 min) and six subjects in series II to 435 mg/m S at rest (30 min) and during exercise of increasing work loads (90 min). The mea.surements of xylene uptake were performed continuously wi,th the Douglas bag technique. In both series, about 60 010 of the amount of xylene supplied to the lungs was taken up. In both series, the concentration in alveolar air was relatively low throughout the entire exposure. The relative concentration in alveolar air displayed a linear correlation to the percentage uptake in the lungs. The ratio between the concentration in arterial blood (mg/kg) and alveolar air (mg/l) amounted to 30-40 at the different work loads. The total amount of xylene expired after the exposure was estimated from the alveolar concentration and alveolar ventilation. In series I, with a total uptake of 1.4 g, the subjects expired about 70 mg, i.e., about 5 010. The corresponding value in series II was 40 mg of a total uptake of 1.0 g, Le., about 4 0/0•

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The amount of body fat in 12 male subjects was determined by means of underwater weighing and anthropometric calculation of skeletal weight. Six subjects (group I) were exposed to 200 ppm of industrial xylene during 30 min of rest and 90 min of exercise at a work load of 50 W. Six subjects (group II) were exposed to 100 ppm for 30 min at rest and during three 3D-min periods of exercise at work loads of 50, 100 and 150 W, respectively. The amount of solvent taken up in the organism was highly correlated to the amount of body fat. When the groups were analyzed together, a correlation was found between the uptake per kilogram of body weight and the alveolar concentrations 4 and 19 h after exposure, even though the groups were exposed under different conditions. However, no correlation was found between total uptake and the alveolar air concentrations after exposure. Needle .biopsies of subcutaneous adipose tissue were taken 0.5, 2, 4 and about 22 h after the end of exposure. Industrial xylene is a mixture of ethylbenzene and 0-, mand p-xylene. The concentrations of ethylbenzene and m-and p-xylene were determined with gas chromatography after evaporation into nitrogen at 150 0 C. Ortoxylene, which constituted 8.8 0/0 of the inspired gas mixture, could not be separated with the column used. Elimination of ethylbenzene-xylene from adipose tissue was slow. The mean concentrations in both groups of subjects were on about the same level after 22 h as during the first 4 h after exposure. In both groups, there was a negative correlation between the concentrations in adipose tissue and the degree of obesity, i.e., obese persons had lower concentrations.

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Exposure to methylene chloride. Content in subcutaneous adipose tissue. by Engström J, Bjurström R