Chromium-based catalysts are used for the synthesis of polyethylene, but little is known about the hazard and biomonitoring possibilities of this type of chromium for workers who may be occupationally exposed to such compounds. In a preliminary study, the bioavailability and toxicokinetics of chromium were studied, in male Wistar rats, after a single intratracheal instillation (2 ml/kg body weight) of various doses (1, 5, 25 mg/kg body weight) of the catalyst (approximately 1% chromium bound to an amorphous silica matrix), either before [CAT-Cr(III)] or after [CAT-Cr(VI)] heat treatment. The results were compared with those of equivalent amounts of two chromium salts (CrCl3 and K2Cr2O7). Each dose group comprised three rats. The concentration of chromium was determined by atomic absorption spectrometry in urine (collected daily for 7 days) and in plasma, erythrocytes, lung and liver tissue obtained at autopsy 7 days after dosing. On the basis of body weights, lung weights and lung histology, there was no overt toxicity, except after the highest dose of CAT-Cr(VI). The elimination of all forms of chromium was rapid and apparently mono-exponential, with calculated half-life elimination times in urine of 4 - 8.5 h for Cr(III) [CAT-Cr(III) and CrCl3] and 8.5 - 21 h for Cr(VI) [CAT-Cr(VI) and K2Cr2O7]. In the erythrocytes, chromium concentrations (on day 7) were significantly increased above control values (3 µg/L) only in rats treated with the two highest doses of Cr(VI) compounds [12 and 64 µg/L for K2Cr2O7, and 14 and 79 µg/L for CAT-Cr(VI)]. The present results suggest that the Cr(VI) catalyst has the same bioavailability and excretion kinetics as a water soluble Cr(VI) salt and that exposure could be monitored by measuring Cr concentrations in urine (shortly after exposure) and in erythrocytes (also at later times points after high exposition). ; status: published