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MANFRED ANKE AN. R. ACAD. NAC. FARM.

Toxicity to Humans

In humans, the threshold level for vanadium toxicity is near 10
(to 20) mg/day. Schroeder et al. (109) administered 4.5 and 9 mg
V/day for 6 to 16 months without apparent detrimental effects; Curran
et al. (33) supplemented 13.5 mg V/day for 6 weeks, with no sign of
intolerance toxicity being found. On the other hand, Somerville and
Davies (116) gave 13.5 mg V/day for 5 months. 40% of the patients
exhibited gastrointestinal disturbances and 40% exhibited green ton-
gues. After intakes of 4.5 to 18 mg V/day over 6 to 10 weeks, the pa-
tients developed green tongues, cramps and diarrhoea (37, 19).

In animals and humans, vanadium generally causes pulmonary
effects of acute vanadium pentoxide inhalation (73, 126), haemato-
logical changes following vanadium exposure (72), and a lowered
cysteine content in hair and nails (122). The coenzyme A content of
the organs is decreased after feeding high doses of vanadium. One
of the compounds involved in the synthesis of coenzyme A is thio-
ethanolamine, which is derived from cysteine by decarboxylation.
Therefore, a decrease in cystine caused by vanadium was presuma-
bly the reason for reduced amounts of coenzyme A. Coenzyme A is
involved in the synthesis of cholesterol, and therefore may affect the
occurrence of atherosclerosis.

In mammals it was shown that vanadium is a strong inhibitor of
Na+ - K+ ATPases (31). This inhibitation is caused by the substitution
of vanadate for phosphate in the ATP-driven reactions (43, 117).
Vanadium pentoxide also seems to open the K-channels of the ery-
throcyte membrane (48, 131). Hemodialysis patients may exhibit
extremely high levels of serum vanadium (123).

TABLE 21. Normative requirement and maximial tolerable intake of vanadium in
man (70 µg/body weight; 350 g/day matter intake/day)

Parameters Normative Maximal

requirement tolerable intake

Vanadium intake, µg/day ~ 10 ~ 3000
Vanadium intake, µg/day body ...., day ~ 0,15 ~ 40
Vanadium, by consumed day matter ~ 30
~ 1000

990