Chromium is present in two main forms - Cr6+ compounds which are man-made and not naturally occurring, and Cr3+ compounds which are present in soil and plants. Industrial chromium toxicity is well-recognised and chromate dust/fumes are a known cause of lung disease and certain types of cancer.12 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 a recognized carcinogen which is rapidly reduced to Cr3+ when it crosses cell membranes and it is thought that an intermediary species in this process may react producing toxic effects including DNA damage.13
Urine chromium concentrations decline rapidly after removal from exposure, but appropriately collected samples are suitable for occupational monitoring.
Chromium is an essential trace element being required for glucose control by potentiating the action of insulin.14 Signs of chromium deficiency are thought to be similar to those found in type 2 diabetes and cardiovascular disease.15 There have been cases of chromium deficiency in patients on total parenteral nutrition whose glucose intolerance was reversed by supplementing with chromium.16,17 Because of its low plasma concentration, contamination from steel needles is a potential problem.
Blood/serum chromium concentrations may also be raised in patients on total parenteral nutrition18 and renal dialysis because of chromium contamination of the fluid used in these treatments. Although a definite increase in serum and in tissue concentrations of chromium can be demonstrated,19 no obvious clinical effect has been noted.
The Food Standards Agency suggest 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. Only around 1% to 2% of ingested chromium is absorbed although absorption from picolinate may be higher. Excretion is mainly via the kidneys and the half-life in blood is about 40 hours and in urine is a few days. The American Conference of Governmental Industrial Hygienists (ACGIH) quotes a Biological Exposure Index for urinary chromium of 10 µg/g creatinine (21.7 nmol/mmol) as an increase during the shift and 30 µg/g creatinine (65.2 nmol/mmol creatinine) at the end of shift at the end of the working week.
Measurement of chromium and cobalt in whole blood is primarily used to assess the viability of metal-on-metal hip replacements. If there is misalignment of ball and cup there may be increased frictional loss of the main metal components. If severe and uncorrected this may cause local tissue damage with formation of a pseudo tumour and necrosis of soft tissue. In April 2010 the Medicines and Healthcare Products Regulation Agency issued an alert recommending their measurement in patients with metal-on-metal prostheses. The most recent update to this guidance was in June 201720. Post-operatively concentrations increase but stabilise within about 1 year. In these patients their concentrations are around 20 to 40 nmol/L but can increase dramatically as a result of wear or corrosion. Concentrations are also affected by exercise and activity and the inclination angle of the femoral cup. Chromium and cobalt may cause local inflammation with possible loosening of the joint, bone loss and tissue damage, all of which may make subsequent repairs difficult. The finding of high concentrations in blood is used to identify those who may develop problems and may indicate increased wear and potential for tissue necrosis.21
Chromium is considered to be a carcinogen in the form of chromates and is on the IARC (International Agency for Research on Cancer) register of carcinogens.22
Recommended Daily Allowance
Males: 30 to 35 µg/day; Females: 20 to 25 µg/day.
Sample Requirements and Reference Ranges for Chromium
|Sample Type||Whole blood, urine (random)|
Urine: universal container
|Precautions||Urine samples for occupational exposure should be taken as random samples at the end of a working shift.|
Whole blood: 300 µL*. (Cobalt can be analysed simultaneously on this volume.)
Urine: 1 mL
Blood: < 40 nmol/L23
MHRA action limit: 135 nmol/L (7 µg/L)20
N.B. MHRA threshold does not apply to stemmed total hip replacementsUrine: < 6.0 nmol/mmol creatinine (STEMDRL derived)
|Mean Turnaround time||Blood: 3.7 days; urine: 5.5 days|
|Method||Inductively coupled plasma mass spectrometry|
Blood: Traceable to reference material produced in accordance with EN ISO 17511:2003 “In vitro diagnostic medical devices. Measurement of quantities in biological samples. Metrological traceability of values assigned to calibrators and control materials”.
Urine: Traceable to reference material produced in accordance with EN ISO 17511:2003 “In vitro diagnostic medical devices. Measurement of quantities in biological samples. Metrological traceability of values assigned to calibrators and control materials” and reference materials with values determined by reference laboratories.
|Intermediate Precision (CV)||
Blood: 5.6% at 233 nmol/L, 3.7% at 446 nmol/L
Urine: 8.5% at 72.4 nmol/L, 2.4% at 347 nmol/L
|Measurement Uncertainty, U||
Blood: 198 ± 16.2 nmol/L, 664 ± 35.2 nmol/L
Urine: 81 ± 15.5 nmol/L, 384 ± 33.8 nmol/L
|Analytical Goals (CV)||Blood: 7%**, Urine: 8%**|
|EQA Scheme||Blood and urine: UK NEQAS, Guildford (once per month)|
* Absolute minimum volume; this volume is insufficient to carry out repeat analysis if analysis fails.
** Goal Origin: STEMDRL state-of-the-art