Carcinogenicity studies chromium toxicity

Chromium in the +3 oxidation state is an essential trace element (see Section 10.3) required for glucose and lipid metabolism in mammals, and a deficiency of it gives symptoms of diabetes mellitus. However, chromium must also be discussed as a toxicant because of its toxicity in the +6 oxidation state, commonly called chromate. Exposure to chromium(VI) usually involves chromate salts, such as Na2Cr04. These salts tend to be water soluble and readily absorbed into the bloodstream through the lungs. The carcinogenicity of chromate has been demonstrated by studies of exposed workers. Exposure to atmospheric chromate may cause bronchogenic carcinoma with a latent period of 10 to 15 years. In the body, chromium(VI) is readily reduced to chromium(III), as shown in Reaction 10.4.3 however, the reverse reaction does not occur in the body. 

Hexavalent chromium compounds have no medical uses and are known as mutagens and carcinogens (19). In an in vitro study the coordination of chromium by picolinate ligands made chromium picolinate more toxic to cultured cells, leading to enhanced apoptosis (20). These observations support the hypothesis that chromium picolinate is a human carcinogen. 

In the following discussion, the toxicity (carcinogenicity) of inhaled strontium chromate is omitted, since its adverse effects are attributed to hexavalent chromium (see Section 3.2.1.7). Unless otherwise stated, the proposed investigations refer to studies of health effects in animals. 

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