WIGAEUS E, LOF A, BJURSTROM R, BYFALT NORDQVIST M. Exposure to styrene: Uptake, distribution, metabolism and elimination in man. Scand j work environ health 9 (1983) 479-488. Eight male subjects were exposed for 2 h to about 2.88 mmol/m3 (300 mg/m3) of styrene vapor during light physical exercise. The uptake of styrene averaged 4.4 mmol, or 68 % of the amount supplied. The arterial blood concentration of styrene reached a relatively stable level of about 20 pmol/l after 75 min of exposure. The calculated value of blood clearance was 1.7 (SD 0.3) l/min, and the extraction ratio about 0.2. The half-time for the elimination phase was 41 (SD 7) min, and the calculated volume of distribution 99 (SD 13) 1. The concentration of styrene in the subcutaneous adipose tissue was about 50 pmol/kg 30-90 min after exposure. The concentration of nonconjugated styrene glycol in blood increased linearly during exposure and was about 15 % of the styrene concentration in blood at the end of exposure. It was eliminated with a halftime of 72 (SD 13) min. Within 28 h after exposure 58 % of the total uptake of styrene was recovered in the urine as mandelic and phenylglyoxylic acid. Their excretion halftimes (0-20 h) were 3.6 (SD 0.4) and 8.8 (SD 1.3) h, respectively. Styrene-7,8-oxide was detected and quantified in blood in a complementary study.
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.
Styrene exposure of 18 workers in fiberglass reinforced plastic industries was measured for 30-min periods throughout each workday for a week. The styrene uptake was estimated using pulmonary ventilation measurements. All urine voidings were collected separately and the styrene metabolites, mandelic acid (MA) and phenylglyoxylic acid (PGA) were determined. The relationship between both exposure and uptake versus excretion of these metabolites was studied. Styrene metabolite concentrations and excretion rates (with 95% tolerance limits) were calculated to correspond to a constant 8-h exposure at the Swedish exposure limit level (25 ppm) or an uptake of an exposure limit related styrene dose (6.3 mmol). The tightest tolerance limits were obtained for excretion rate of MA + PGA per 24 h. The calculated biological exposure limit was 3.4 (+/- 0.7) mmol MA + PGA/24h for a dose of 6.3 mmol styrene.
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