Chromium

Chromium is an abundant earth element. It exists in two main oxidation states, Cr(III) and Cr(VI), which differ greatly in their chemical properties. Cr(III) is ubiquitous in nature, and is thought to be of use in humans as a component of a glucose tolerance factor, needed to potentiate the actions of insulin. Chromium deficiency in patients on long term TPN has been linked with adult onset diabetes. The UK recommended daily intake of Cr(III) is 25 µg/day for adults and 0.1-1.0 µg/kg/day for children.

Cr(VI) is a highly corrosive, strong oxidising agent, used widely in industry. Significant dermal absorption can occur following acute dermal exposure, leading to renal tubular damage. Chronic dermal exposure can cause ulceration. Perforation of the nasal septum has been reported through chronic inhalation of Cr(VI) compounds. There is an increased risk of malignancy in such cases. Iatrogenic toxicity through over-supplementation of patients on TPN is known.

To assess acute exposure, whole blood or urine can be analysed. For assessing supplementation with chromium, plasma is preferred, and for occupational exposure, urine is best analysed. In all cases, extra care should be taken to avoid chromium contamination. A large number of hip replacements are carried out in the UK every year (>50,000), with the Metal-on-Metal (MoM) type gaining in popularity.

The Medical Devices Alert (MDA/2012/008) issued in February 2012 by the MHRA has, however, highlighted that MoM prosthesis failure in some patients may arise from localised tissue reactions associated with the release of particulate metal ions during articulation. Cobalt (Co) and Chromium (Cr) are the key components in the metallic alloy used in the manufacture of these MoM prostheses: The MHRA has thus recommended following up patients who have undergone MoM hip replacement on an annual basis for at lease 5 years, with the measurement of Co and Cr carried out in symptomatic/suspected patients. The MDA document outlines a plan of action based on the concentrations measured.