Nutritional interest in chromium is based on studies suggesting the existence of a chromium-containing glucose tolerance factor that is important in potentiating the action of insulin. Signs of chromium deficiency are thought to be similar to those found in type 2 diabetes and cardiovascular disease. However, clear proof of the essentiality of chromium in humans has been difficult to attain, partly because of the difficulties of measuring chromium at the very low levels found in body fluids. The Food Standards Agency recommend a daily intake of 25 µg/day for adults but advise against the use of chromium picolinate which is widely marketed as an aid to weight loss.
Chromium is present in two main forms – Cr6+ compounds, some of which are carcinogenic, and Cr3+ compounds which are not considered to be harmful. Industrial chromium toxicity is well recognised and chromate dust/fumes are a known cause of lung disease and certain types of cancer. Welders of special steels are known to be exposed to Cr6+ fume. Chromates are also used with arsenic and copper in wood preservatives and workers involved in this process should be monitored for chromium as well as arsenic. The urinary excretion of total chromium is directly related to the inhalation and absorption of water soluble Cr6+ in dust or fumes. Cr6+ is rapidly reduced to Cr3+ when it crosses cell membranes and it is thought that an intermediary species in this process may react to produce toxic effects including interaction with genetic material.
Serum chromium may be raised in patients on total parenteral nutrition and renal dialysis because of slight chromium contamination of the fluid used in these treatments. Although a definite increase in serum and in tissue concentrations of chromium can be demonstrated, no obvious clinical effect has been noted.
Measurement of chromium and cobalt in whole blood is used to assess the viability of prosthetic implants.
Sample Requirements and Reference Ranges for Chromium
| Sample Type | Whole blood, random urine |
|---|---|
| Container | EDTA, universal container |
| Precautions | Urine samples for occupational exposure should be taken as random samples at the end of a working shift. |
| Minimum volume* | Whole blood: 250 µL Urine: 1 mL |
| Reference ranges | |
| - whole blood | < 40 nmol/L MHRA action limit: 135nmol/L (7 µg/L) |
| - urine | < 6.0 nmol/mmol creatinine |
| Turnaround time | 2 weeks |
| Method | Urine: Graphite furnace/atomic absorption spectrometry
Blood: Inductively coupled plasma mass spectrometry |
* This is the absolute minimum volume; these volumes are insufficient to carry out a repeat analysis in the event of an analytical problem.