Chemistry Reference
In-Depth Information
CHAPTER
46
Vanadium
BIRGITTA J-SON LAGERKVIST AND AGNETA OSKARSSON
ABSTRACT
Vanadate has been shown to inhibit Na
+
-K
+
-ATPase,
phosphatases and several other enzyme systems.
Vanadium compounds enhance the effects of insulin
and have been shown to lower blood glucose in animal
and human experiments in diabetic individuals. Both
acute and chronic effects of occupational exposure
to vanadium pentoxide (V
2
O
5
) and other vanadium
compounds have been described. They are manifest-
ed mainly as delayed, but reversible irritation of the
respiratory tract involving excess mucus production
and prolonged coughing, accompanied by bronchos-
pasm, wheezing, and diarrhea in cases of more severe
exposure. Eye irritation and conjunctivitis have been
reported in workers. Tracheobronchitis may result from
heavy, long-term exposure. Changes in lung function
indicating obstruction and an increase in infl ammatory
biomarkers have been demonstrated in boiler cleaners
after prolonged exposure. Vanadium is not mutagenic
in Ames test. However, pentavalent and tetravalent
vanadium compounds have produced aneuploidy in
somatic cells
in vitro
and
in vivo
. A clear evidence of car-
cinogenic activity has been shown in mice after inhala-
tion of vanadium pentoxide. The International Agency
for Research on Cancer (IARC) has classifi ed vana-
dium as a possible carcinogen (Group 2B). Biological
monitoring of vanadium in serum, blood, and urine is
used to follow exposure to vanadium compounds in
occupational and population studies. Urine analysis,
being a noninvasive method, is suitable for monitoring
of workers. Reviews on environmental, toxicological
and occupational health aspects of vanadium have
been published by IPCS (1988), ATSDR (1992), Domin-
go (1996), WHO (1996), IPCS (2001), Barceloux (1999),
HSE (2002), and EFSA (2004).
Absorption of vanadium from the gastrointestinal
tract is poor, not exceeding 2% in humans. Soluble
compounds of vanadium are absorbed to a considera-
ble extent after inhalation and concentrated in the lung,
but available information is not adequate for a reliable
estimation of dose-response relationships. Absorbed
vanadium is widely distributed in the body. In animals
the highest values are found in bone, kidney, liver, and
spleen. Bone maintains essentially unchanged levels for
several weeks. Low concentrations have been detected
in brain and in animal placenta and testes. Urine is the
dominating route of excretion of absorbed vanadium.
Animal and human data indicate that excretion occurs
in at least two phases. A three-compartment model for
elimination is described in humans with half-times
after intravenous injection of 1.2 hours, 26 hours, and
10-12 days. Vanadium is essential for certain bacteria
and microorganisms. Some reports suggest that va-
nadium is essential for mammals, but no biochemical
function has been defi ned in humans. The total dietary
intake is estimated to be 6-30 and in some regions up
to 50
g/day. The use of vanadium salts as a supple-
ment in athletes and body builders has been reported.
Local effects in experimental animals are mainly seen
in the respiratory tract. They may be acute and chronic,
including bronchitis and pneumonia. Systemic effects
have been observed in liver, kidney, nervous system,
cardiovascular system, and blood-forming organs.
Metabolic effects include interference with the bio-
synthesis of cystine and cholesterol, depression and
stimulation of phospholipid synthesis and, at higher
concentrations, inhibition of serotonin oxidation.
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