TOXICOLOGICAL PROFILE FOR CHROMIUM - Davidborowski.com

CHROMIUM 1232. HEALTH EFFECTSdiffusion through non-specific anion channels (similarly to phosphate and sulfate anions). Absorption ofchromium(III) compounds is via passive diffusion and phagocytosis. Absorption of inhaled chromiumcompounds takes place in the lung via transfer across cell membranes and in the gastrointestinal tractfrom particles cleared from the lungs. Absorption after oral exposure in humans varies from essentiallynone for the highly insoluble chromium(III) compound chromic oxide, to 0.5–2.0% for chromium(III)compounds in the diet, to approximately 2–10% for chromium(VI) as potassium chromate. Dermalabsorption depends on the physical and chemical properties of the compound, the vehicle, and theintegrity of the skin. Concentrated solutions of chromium(VI) compounds such as potassium chromatecan cause chemical burns and facilitate absorption. Once in the blood, chromium compounds aredistributed to all organs of the body. Particles containing chromium can be retained in the lung for yearsafter occupational exposure. Chromium(VI) is unstable in the body and is reduced to chromium(V),chromium(IV), and ultimately to chromium(III) by many substances including ascorbate and glutathione.It is believed that the toxicity of chromium(VI) compounds results from damage to cellular componentsduring this process (e.g., generation of free radicals). There is also evidence in in vitro experiments thatchromium(III) can be reduced to chromium(II) and exert toxic effects. Absorbed chromium is excretedprimarily in urine, the half-time for excretion of chromium administered as potassium chromate isestimated to be 35–40 hours in humans. Hair and nails are minor pathways of excretion.2.3.1 Absorption2.3.1.1 Inhalation ExposureThe absorption of inhaled chromium compounds depends on a number of factors, including physical andchemical properties of the particles (oxidation state, size, solubility) and the activity of alveolarmacrophages.The identification of chromium in urine, serum and tissues of humans occupationally exposed to solublechromium(III) or chromium(VI) compounds in air indicates that chromium can be absorbed from thelungs (Cavalleri and Minoia 1985; Gylseth et al. 1977; Kiilunen et al. 1983; Mancuso 1997b; Minoia andCavalleri 1988; Randall and Gibson 1987; Tossavainen et al. 1980). In most cases, chromium(VI)compounds are more readily absorbed from the lungs than chromium(III) compounds, due in part todifferences in the capacity to penetrate biological membranes. Nevertheless, workers exposed tochromium(III) lignosulfonate dust at 0.005–0.23 mg chromium(III)/m 3 had clearly detectableconcentrations of chromium in the urine at the end of their shifts. Based on a one compartment kinetic