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Trace
Elements Laboratory |
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A
Joint Venture of London Health Sciences Centre and St. Joseph's
Health Care London
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Chromium (Cr)
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| Atomic
Number: |
24 |
| Atomic
Symbol: |
Cr |
| Atomic
Weight: |
51.996 |
| Electron
Configuration: |
[Ar]4s13d5 |
| TITLE |
Chromium (Cr) |
| SYNONYMS/FORMS
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Metal
Chromium (Cr ), Compounds of Cr (III) and Cr (VI) |
| GENERAL
INFORMATION |
Chromium exists primarily in two valence states, trivalent
Cr(III) and hexavalent Cr(VI).
Cr(III) is an essential nutrient necessary for glucose and
lipid metabolism. It enhances insulin activity by forming
a complex with insulin (1). Cr(III) deficiency has been shown
to lead to symptoms similar to that of diabetes with an impaired
glucose tolerance. The estimated safe and adequate daily dietary
intake (ESADDI) for 7 years-adults is 50 to 200 µg and
for children 0-6 years is 10 to 40 µg (2). There is
no evidence of detrimental effects of supplemental chromium
at intakes up to 1000 ug/day (2).
Cr(VI)
is a toxic form and certain Cr(VI) compounds produced industrially
have been recognized as lung carcinogens (2). Cr(VI) is
better absorbed than Cr(III). Once absorbed into blood,
Cr(VI) enters the red blood cells where it is reduced to
Cr(III) which binds to hemoglobin. After exposure, Cr concentrations
in red blood cells remain elevated for weeks, while plasma
concentrations return to baseline values within days. About
80% of absorbed Cr is excreted in urine and its excretion
is rather rapid.
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SOURCES/ROUTE
OF EXPOSURE
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Principle industrial users of Cr compounds are the metallurgical
processors of ferrochromium and stainless steel, electroplating,
wood tanalising, pigment production and leather tanning. The
major routes of occupational exposure are inhalation and skin
contact of industrial hexavalent chromium (CrO3). Non-occupational
exposure occurs mainly by ingestion of foods containing Cr(III)
supplements and drinking well-water contaminated with chromium
picolinate. |
| TOXICITY
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Most toxic effects occur in an occupational setting when workers
are exposed to Cr(VI) compounds that can be absorbed by the
lung and GI tract and to a less extent by skin contact. Symptoms
include cough, chest tightness, wheeze, irritation of mucous
membranes and skin, ulceration and nasal septum perforation
and kidney damage. Cr(VI) is a known carcinogen implicated
in lung cancer (4). |
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MONITORING/CLINICAL
INTERPRETATION
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Chromium
(III) is provided as a supplement in total parenteral nutrition
(TPN). Patients on long-term TPN should be monitored regularly
to avoid TPN overload.
Chromium
concentrations in erythrocytes, whole blood, plasma and
urine may be elevated in individuals with metallic prosthetic
joints due to wear and corrosion of orthopaedic implants.
The clinical significance of elevated metal ion levels has
not been fully understood. However, evidence has shown that
highly elevated blood levels are probably associated with
high wear at the bearing, implant dysfunction, and adverse
tissue reactions to metal debris.
UK
MHRA Threshold for individuals with metallic hip replacement
(5)
Chromium in blood: 7 ug/L (134.6 nmol/L)
ACGIH
Biological Exposure Index (6)
Chromium in urine (end of shift at end of workweek): 25
ug/L (480.7 nmol/L)
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| MATRIX
CHOICE |
For
monitoring Cr levels following orthopedic arthroplasty, whole
blood is the recommended sample because it does not need to
be separated or transferred into a secondary tube after draw,
and the primary collection tube can be sent directly for testing.
This avoids possible sample contaminations from additional
sample process steps.
Plasma
and erythrocyte Cr concentrations can be used for nutritional
assessment in patients on TPN. Plasma concentration reflects
day-to-day Cr variations. The measurement of Cr in erythrocytes
provides a better index of body content than the measurement
of Cr in plasma.
Note:
If serum is requested for analysis, the sample must be spun
and separated from blood cells within 30 minutes. Because
Cr concentration is much higher in erythrocytes than in
serum, Cr will be released from erythrocytes resulting in
falsely elevated levels in serum if not separated within
30 minutes or hemolysis occurs.
Random urine is recommended for occupational monitoring.
Hair can be used for chronic exposure.
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| TREATMENT
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No proven antidote is available for chromium poisoning.
Remove from exposure in industrial setting, and rely on the
urinary and fecal clearance of the body burden. |
| REFERENCES |
1.
http://www.atsdr.cdc.gov/tfacts7.html
2. National Research Council: Recommended Dietary Allowance,
10th ed. Washington, DC. National Academy Press, 1989.
3. Anderson, R.A. Chromium as an Essential Nutrient, The Chromium
File (1999) Issue No. 6 http://www.chromium-asoc.com/publications/crfile6sep99.htm
4. Aw, T-C. Biological Monitoring and Health Surveillance
for Workers Exposed to Chromium Chemicals in Chromate Ore
Processing, The Chromium File (2004) Issue No.10 http://www.chromium-asoc.com/publications/crfile10apr04.htm
5. Metal-on-metal hip replacement and hip resurfacing arthroplasty.
What does the MHRA medical device alert mean? http://www.jisrf.org/pdf_files/MoM_BOA-BHS_AdvicetoSurgeons_1.pdf
6. ACGHI (American Conference of Governmental Industrial Hygienists).
Threshold Limit Values for Chemical Substances and Physical
Agents & Biological Exposure Indices, 2008. |
Sample Requirements
(click on cell)
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