TOXICOLOGICAL PROFILE FOR CHROMIUM - Davidborowski.com

CHROMIUM 132. HEALTH EFFECTS2.1 INTRODUCTIONThe primary purpose of this chapter is to provide public health officials, physicians, toxicologists, andother interested individuals and groups with an overall perspective on the toxicology of chromium. Itcontains descriptions and evaluations of toxicological studies and epidemiological investigations andprovides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.A glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile.Chromium is a naturally occurring element found in animals, plants, rocks, and soil and in volcanic dustand gases. Chromium has oxidation states (or "valence states") ranging from chromium(-II) tochromium(VI). Elemental chromium (chromium(0)) does not occur naturally. Chromium compounds arestable in the trivalent state and occur in nature in this state in ores, such as ferrochromite. The hexavalent(VI) form is the second-most stable state. However, chromium(VI) rarely occurs naturally, but is usuallyproduced from anthropogenic sources (EPA 1984a).Trivalent chromium compounds, except for acetate, nitrate, and chromium(III) chloride-hexahydrate salts,are generally insoluble in water. Some hexavalent compounds, such as chromium trioxide (or chromicacid) and the ammonium and alkali metal (e.g., sodium, potassium) salts of chromic acid are readilysoluble in water. The alkaline metal (e.g., calcium, strontium) salts of chromic acid are less soluble inwater. The zinc and lead salts of chromic acid are practically insoluble in cold water. Chromium(VI)compounds are reduced to chromium(III) in the presence of oxidizable organic matter. However, innatural waters where there is a low concentration of reducing materials, chromium(VI) compounds aremore stable (EPA 1984a). For more information on the physical and chemical properties of chromium,see Chapter 3.In humans and animals, chromium(III) is an essential nutrient that plays a role in glucose, fat, and proteinmetabolism by potentiating the action of insulin (Anderson 1981). The biologically active form ofchromium, called glucose tolerance factor (GTF), is a complex of chromium, nicotinic acid, and possiblyamino acids (glycine, cysteine, and glutamic acid). Both humans and animals are capable of convertinginactive inorganic chromium(III) compounds to physiologically active forms. The nutritional role ofchromium is further discussed in Section 2.3.3. Although chromium(III) has been reported to be an