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IntroductionAtomic mass 52. Chromium occurs as its oxide in chromite ore that also contains various amounts iron, aluminium and manganese. Chromium compounds adopt three oxidation states, 3+, 4+ and 6+. The oxidation state determines toxicity, metabolism and excretion.ExposureChromium is present in a normal diet at trace (but essential) levels. Occupational exposure is related to the industrial uses of chrome compounds in production and use of steels, pigments, leather tanning and wood preservation solutions, plating chemicals, and cement.Chromium is present in solutions used for total parentral nutrition as a contaminant. The use of such unsupplemented solutions has been reported to be associated with elevated serum chromium. The use of supplemented solutions (0.2 mg/kg) has been associated with serum chromium levels twenty-fold greater than controls. AbsorptionCutaneous absorption of hexavalent forms has been demonstrated. Pulmonary absorption is related to water solubility. Very little chromium is absorbed in the gut.DistributionChromium is oxidised or reduced to yield the chromium 3 ion that circulates as a transferrin complex. Chromium is distributed diffusely in the body with generally higher levels found in kidney, liver, spleen and blood. Chromium does not appear to cross the blood-brain barrier.ExcretionChromium is primarily excreted in the urine, a finding that accounts for the accumulation of the metal seen in renal failure.PathologyToxicity is predominantly associated with industrial exposures. Hexavalent chromium compounds appear to have greatest toxicity, exposure resulting in irritation of skin and membranes. The most common presentation is an allergic eczema primarily on the skin but occasionally in the lungs. Some types of industrial exposure have been linked to increased prevalence of lung cancers. Acute exposure to high chromium concentrations can cause renal damage.MonitoringMonitoring of industrial exposures is best carried out by urine determination. The chromium absorbed demonstrates three clear half-lives of 7 hours, 20 days and 4 years. This should be taken into consideration when interpreting the data. It is recommended to estimate risks by estimating exposure rather than attempting to track absorbed chromium.Chromium is an essential micronutrient and is suspected of playing a role in glucose tolerance. Impaired glucose tolerance has been reported in cases of suspected chromium deficiency. Normal serum chromium is at the limit of detection of current analytical systems. Where chromium is consistently undetectable there may be a case for cautious supplementation. Normal serum chromium levels are probably less than 8 nmol/L. Samples taken for determination are notoriously prone to contamination by the collection equipment and storage tubes. Reference intervals at PaLMS Trace Element Service have been calculated to account for contamination present in the commercial collection tubes supplied by PaLMS. Please contact the laboratory for more information on the detection of presumed deficiency or collection procedures. The monitoring of elevated serum chromium in renal disease or after uncontrolled supplementation, or urine chromium is not compromised. TreatmentRecommended supplementation is 5-10 ug of chromic chloride daily for three days followed by 10 ug weekly. Monitor improvement in glucose tolerance.AnalysisSerum and urine chromium are determined by graphite furnace atomic absorption spectrometry. Other matrices are determined by inductively coupled plasma mass spectrometry. |