TOXICOLOGICAL PROFILE FOR CHROMIUM - Davidborowski.com

CHROMIUM 1642. HEALTH EFFECTSthe bloodstream than is chromium(III) (Gao et al. 1993; Suzuki et al. 1984). Chromium that is notabsorbed in the lungs may be cleared via mucociliary clearance and enter the gastrointestinal tract.Chromium is poorly absorbed from the gastrointestinal tract; the primary site of chromium absorptionappears to be the jejunum (Donaldson and Barreras 1966). The bioavailability of chromium compoundsseems to be most dependant on the oxidation state of the chromium atom. However, other factors,including dose level and formulation of the chromium, can influence the extent of absorption.Chromium(III) is very poorly absorbed, with only 0.5–2.8% of dietary chromium absorbed via thegastrointestinal tract of humans (Anderson 1986; Anderson et al. 1983; Donaldson and Barreras 1966;Gargas et al. 1994; Kerger et al. 1996a; Kuykendall et al. 1996). Chromium(III) absorption efficiencyappears to be related to dietary intake; the efficiency decreases with increasing dose (Anderson 1986;Anderson et al. 1983). Human studies demonstrate that chromium(VI) is effectively reduced tochromium(III) by gastric juices (De Flora et al. 1987a) and in general, chromium(VI) is better absorbedthan chromium(III) following oral exposure in humans (Donaldson and Barreras 1966; Finley et al.1996b; Kerger et al. 1996a; Kuykendall et al. 1996). Absorption efficiencies ranging from 1.7 to 6.9%have been estimated in humans (Finley et al. 1996a; Kerger et al. 1996a, 1997; Kuykendall et al. 1996).Unlike chromium(III), absorption efficiency appears to increase with dose; Kerger et al. (1997) estimatedan efficiency of 1.7% at 0.05 mg chromium(VI)/kg/day and 3.4% at 0.1 mg chromium(VI)/kg/day.Ingestion of chromium with a meal appears to increase the absorption efficiency (Chen et al. 1973).Both chromium(III) and chromium(VI) can penetrate human skin to some extent, especially if the skin isdamaged. Following dermal exposure, chromium has been detected in the blood, feces, and urine ofexposed humans (Brieger 1920), though in this study, the skin was damaged, which likely facilitatedabsorption. An average rate of systemic uptake of chromium(VI) in humans submersed in chlorinatedwater containing potassium dichromate(VI) for 3 hours was 1.5x10 -4 µg/cm 2 -hour (Corbett et al. 1997).Chromium(VI) appears to penetrate the skin faster than chromium(III) (Mali et al. 1963; Spruit and vanNeer 1966; Wahlberg 1970), though many other factors may be involved, including solvent (Liden andLundberg 1979) and concentration (Baranowska-Dutkiewicz 1981).Absorbed chromium is carried throughout the body in the blood, eventually being distributed to alltissues. Greatest concentrations of chromium are found in the blood, liver, lung, spleen, kidney, and heart(Kaufman et al. 1970; Schroeder et al. 1962; Teraoka 1981). Because insoluble chromium is notcompletely cleared or absorbed following inhalation exposure, greater levels of chromium are often foundin lung tissues following inhalation of chromium compounds than following other methods of exposure.