[Effects of chromium compounds on the respiratory system. 2. Difference between water-soluble hexavalent and trivalent compounds].

Transference and transformation of chromium compounds, known as occupational carcinogens, in the lung of rats were studied by determining blood chromium levels after a single mist inhalation or an intravenous injection of water-soluble chromic acid (hexavalent) and chromium chloride (trivalent). Conclusion drawn from this study are as follows: Transference of chromium from the lung to the blood stream is ended quickly after the inhalation of chromic acid mist. Alveolar permeability of hexavalent chromic acid is much higher than that of trivalent chromium chloride. The greater part of the transferred chromium in the blood after the inhalation of chromic acid mist is not transformed to any other form; therefore, it seems to be present as the hexavalent form. The hexavalent chromic acid in the blood diffused to the liver, kidneys and the spleen, but the trivalent chromium chloride distributed only in the blood. The hexavalent chromic acid in the blood decreased more slowly than the trivalent chromium chloride. The biological half-time of the chromic acid in the blood was about 60 hours, whereas that of the chromium chloride was only about 2 hours. These results suggest that the water-soluble hexavalent chromium compounds may be apparently different from the trivalent chromium compounds in the transference from the lung and following distribution in the body. These differences might be caused by the high permeability through the cell membrane in hexavalent chromium compounds and the high possibility of binding with proteins in trivalent chromium compounds.