For more information on the physical and chemical properties of chromium, see Chapter 4. However, in natural waters where there is a low concentration of reducing materials, chromium(VI) compounds are more stable ( EPA 1984a). Chromium(VI) compounds are reduced to chromium(III) in the presence of oxidizable organic matter. The zinc and lead salts of chromic acid are practically insoluble in cold water. The alkaline metal (e.g., calcium, strontium) salts of chromic acid are less soluble in water. Some hexavalent compounds, such as chromium trioxide (or chromic acid) and the ammonium and alkali metal (e.g., sodium, potassium) salts of chromic acid are readily soluble in water. Trivalent chromium compounds, except for acetate, nitrate, and chromium(III) chloride-hexahydrate salts, are generally insoluble in water. However, chromium(VI) rarely occurs naturally, but is usually produced from anthropogenic sources ( EPA 1984a). The hexavalent (VI) form is the second-most stable state.
Chromium compounds are stable in the trivalent (III) state and occur in nature in this state in ores, such as ferrochromite. Elemental chromium (chromium(0)) does not occur naturally. Chromium has oxidation states (or "valence states") ranging from chromium(-II) to chromium(VI). It contains descriptions and evaluations of toxicological studies and epidemiological investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.Ī glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile.Ĭhromium is a naturally occurring element found in animals, plants, rocks, and soil and in volcanic dust and gases. The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of chromium.
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