INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 81
VANADIUM
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policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization.
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the International Labour Organisation,
and the World Health Organization
World Health Orgnization
Geneva, 1988
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR VANADIUM
1. SUMMARY AND CONCLUSIONS
1.1. Identity, physical and chemical properties, analytical methods
1.2. Sources in the environment, environmental transport and
distribution
1.3. Environmental levels and human exposure
1.4. Kinetics and metabolism
1.5. Effects on experimental animals and in vitro test systems
1.6. Effects on man
1.6.1. Local effects and dose-response relationships
1.6.2. Systemic effects and dose-response relationships
1.7. Evaluation of health risks for man
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1. Identity
2.2. Physical and chemical properties
2.3. Analytical methods
2.3.1. Atomic absorption analysis and emission spectrometry
2.3.2. Neutron activation analysis
2.3.3. Spark-source mass spectrometry
2.3.4. Spectrophotometric analysis
2.3.5. Electrochemical methods
2.3.6. Chromatography
3. SOURCES IN THE ENVIRONMENT, ENVIRONMENTAL TRANSPORT AND DISTRIBUTION
3.1. Natural occurrence
3.1.1. Rocks
3.1.2. Soils
3.1.3. Water
3.1.4. Air
3.1.5. Plants
3.1.6. Animals
3.2. Man-made sources
3.2.1. Production levels and processes
3.2.1.1 Extraction from ores
3.2.1.2 Extraction from fossil fuels
3.2.1.3 Extraction from slag
3.3. Consumption and use
3.3.1. Metallurgy
3.3.2. Other industries
3.4. Environmental pollution resulting from production, use, and
waste disposal
3.4.1. Metallurgy
3.4.2. Fossil fuel combustion
3.4.3. Agriculture
3.5. Transport and transformation
3.5.1. Geochemical processes
3.5.2. Biogeochemical processes
3.5.2.1 Transport in, and removal from, water
3.5.2.2 Occurrence in hydrocarbons
3.5.2.3 Biospheric redox processes
3.5.2.4 Transport in air
4. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
4.1. General population exposure
4.1.1. Air
4.1.2. Water
4.1.3. Food
4.1.3.1 Individual foods
4.1.3.2 Complete diets
4.2. Occupational exposure
4.2.1. Metallurgy
4.2.2. Cleaning of oil-fired boilers
4.2.3. Occupational exposure limits
5. KINETICS AND METABOLISM
5.1. Physiological role
5.1.1. Microorganisms
5.1.2. Animals
5.2. Absorption
5.2.1. Absorption by inhalation
5.2.1.1 Human studies
5.2.1.2 Animal studies
5.2.2. Absorption from the gastrointestinal tract
5.2.2.1 Human studies
5.2.2.2 Animal studies
5.2.3. Absorption through the skin
5.3. Distribution and transformation
5.3.1. Human studies
5.3.2. Animal studies
5.4. Retention
5.4.1. Human studies
5.4.2. Animal studies
5.5. Elimination
5.5.1. Human studies
5.5.2. Animal studies
6. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
6.1. Aquatic organisms
6.1.1. Microorganisms and higher plants
6.1.2. Invertebrates
6.1.3. Fish
6.2. Terrestrial organisms
6.2.1. Uptake of vanadium by plants
6.2.2. Effects on plants
7. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS
7.1. General toxicity
7.2. Effects on metabolic processes
7.2.1. Mechanisms of action
7.3. Effects on the nervous system
7.4. Effects on the respiratory system
7.5. Effects on the cardiovascular system
7.6. Effects on the kidney
7.7. Effects on the immune system
7.8. Reproduction, embryotoxicity, and teratogenicity
7.8.1. Reproduction and embryotoxicity
7.8.2. Teratogenicity
7.9. Mutagenicity and related end-points
7.10. Carcinogenicity
8. EFFECTS ON MAN
8.1. Therapeutic exposure and controlled studies
8.1.1. Therapeutic exposure
8.1.2. Controlled studies
8.1.2.1 Effects on metabolism
8.1.2.2 Effects on the respiratory system
8.2. Clinical studies
8.2.1. Acute toxicity
8.2.2. Chronic toxicity
8.2.3. Diagnosis
8.2.4. Treatment of poisoning
8.3. General population exposure
8.3.1. Low vanadium intake
8.3.2. Epidemiological studies
8.4. Occupational exposure
8.4.1. Metallurgy
8.4.2. Cleaning and related operations on oil-fired boilers
8.4.3. Handling of pure vanadium pentoxide or vanadate dusts
8.4.4. Other industries
9. EVALUATION OF HEALTH RISKS FOR MAN
9.1. Environmental levels and exposures
9.2. Physiological role
9.3. Effects and dose-response relationships
9.3.1. Local effects and dose-response relationships
9.3.2. Systemic effects and dose-response relationships
9.3.2.1 Metabolic effects
9.3.2.2 Effects on the nervous system
9.3.2.3 Effects on the liver
9.3.2.4 Effects on the kidney
9.3.2.5 Cardiovascular effects
9.3.2.6 Pulmonary effects
9.3.2.7 Effects on the immune system
9.3.3. Reproduction, embryotoxicity, and teratogenicity
9.3.4. Mutagenicity
9.3.5. Carcinogenicity
9.3.6. Risks from exposure of the general population
10. RECOMMENDATIONS
REFERENCES
WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR VANADIUM
Members
Professor A.D. Dashash, Department of Community Medicine,
Medical Faculty, University of Damascus, Damascus, Syria
(Chairman)
Dr R. Frentzel-Beyme, German Cancer Research Centre, Institute
of Epidemiology and Biometry, Heidelberg, Federal Republic
of Germany
Mrs Chantana Jutiteparak, Technical Division, Food and Drug
Administration, Ministry of Public Health, Bangkok,
Thailand
Professor G.N. Krasovsky, Department of Water, Hygiene and
Sanitary Waterbodies Protection, A.N. Sysin Research
Institute of General and Community Hygiene, Moscow, USSR
Dr G.D.E. Njagi, Genotoxicology Unit, Botany Department,
Kenyatta University, Nairobi, Kenya (Rapporteur)
Dr H. Nordman, Clinical Section, Institute of Occupational
Health, Helsinki, Finland
Professor A.V. Roshchin, Department of Occupational Hygiene,
Central Institute for Advanced Medical Training, Moscow,
USSR (Vice-Chairman)
Professor Sun Mian Ling, Department of Environmental Hygiene,
School of Public Health, West China University of Medical
Sciences, Chengdu, China
Representatives from Other Organizations
Dr Z.P. Grigorevskaya, Centre for International Projects, USSR
State Committee for Science and Technology, Moscow, USSR
Dr G.F. Shkolenok, International Register of Potentially Toxic
Chemicals, United Nations Environment Programme, Geneva,
Switzerland
Observers
Professor V.Yu. Kogan, Institute for General Hygiene and Prof-
pathology, Yerevan, Armenia, USSR
Dr S.M. Sokolov, Minsk Medical Institute, Minsk, USSR
Secretariat
Dr E. Smith, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland (Secretary)
Dr M. Gounar, Centre for International Projects, USSR State
Committee for Science and Technology, Moscow, USSR
NOTE TO READERS OF THE CRITERIA DOCUMENTS
Every effort has been made to present information in the
criteria documents as accurately as possible without unduly
delaying their publication. In the interest of all users of the
environmental health criteria documents, readers are kindly
requested to communicate any errors that may have occurred to
the Manager of the International Programme on Chemical Safety,
World Health Organization, Geneva, Switzerland, in order that
they may be included in corrigenda, which will appear in
subsequent volumes.
* * *
A legal file can be obtained from the International Register
of Potentially Toxic Chemicals, Palais des Nations, 1211 Geneva
10, Switzerland (Telephone No. 988400 - 985850).
ENVIRONMENTAL HEALTH CRITERIA FOR VANADIUM
A WHO Task Group on Environmental Health Criteria for
Vanadium met in Moscow, USSR from 30 March to 3 April 1987.
Dr M.I. Gounar opened the meeting and greeted the members on
behalf of the Centre for International Projects, Moscow, USSR.
Dr E. Smith addressed the meeting on behalf of the three co-
operating organizations of the IPCS (ILO/UNEP/WHO). The Task
Group reviewed and revised the draft criteria document and made
an evaluation of the health risks of exposure to vanadium.
The efforts of all those who helped in the preparation and
finalization of the document are gratefully acknowledged.
* * *
Partial financial support for the publication of this
criteria document was kindly provided by the United States
Department of Health and Human Services, through a contract from
the National Institute of Environmental Health Sciences,
Research Triangle Park, North Carolina, USA - a WHO
Collaborating Centre for Environmental Health Effects.
Financial support was also generously provided by the Institute
of Occupational Health, Helsinki, Finland - an IPCS
Participating Institution.
1. SUMMARY AND CONCLUSIONS
1.1 Identity, Physical and Chemical Properties, Analytical Methods
Vanadium (V) is a greyish metal that occurs in the form of
two natural isotopes 50V and 51V. It forms oxidation states of
-1, 0, +2, +3, +4, and +5, the oxidation states +3, +4, and +5
being the most common. Oxidation state +4 is the most stable.
Vanadium pentoxide (V2O5) is the most common commercial form of
vanadium. It dissolves in water and acids and forms vanadates
with bases. Vanadium in the +3 oxidation state (e.g., V2O3) is
basic and dissolves in acid forming a green hexa-aquo ion.
Vanadium+3 salts are strong reducing agents. Organic compounds
of vanadium are generally unstable.
Analytical methods have improved during recent years, and
extremely small amounts of vanadium can be detected in various
media. Atomic absorption assays are suitable for the routine
determination of vanadium in different media. Some refractory
oxides do not dissociate in flame. Sensitivity can be improved
by the use of a high temperature oxyacetylene flame. Flameless
atomic absorption for the determination of vanadium in air has a
detection limit of 1 µg/litre. The same method can also be
used for the determination of vanadium in water and biological
samples, with a detection limit of 0.1 - 0.4 ng. Inductively
coupled plasma optical emission spectrometry has proved an
accurate and scientific development of atomic absorption.
Neutron activation analysis, which is both rapid and
accurate, has been successfully used for the determination of
vanadium in biological fluids, such as serum and blood, and in
air, water, and biological materials. The quantitative
separation of the components to be analysed is not necessary
with this method. The detection limit of neutron activation
assays is lower than that of atomic absorption methods, and
vanadium in air can be determined at a level of 10-12 g.
Spark-source mass spectrometry is suitable for the
simultaneous determination of several elements in air and
biological materials and has a detection limit of 10-11 -
10-12 g. Neutron activation and spark-source mass spectrometry
are sophisticated methods that, because of their high cost, are
not always feasible. Various electrochemical and spectrophoto-
metric assays are being widely used for the determination of
vanadium in a variety of media. These methods have the
advantage of being relatively cheap. Coulometric titration and
controlled potential coulometry are accurate methods for the
determination of vanadium in solutions. They are not as
sensitive as the more sophisticated methods.
Stripping voltammetry and other modern modifications of
polarography, as well as electrometrical methods based on
catalytic reactions, are considered highly sensitive for the
determination of vanadium in solutions and biological materials;
however, depending on the composition of the sample, they could
involve operations to separate out interfering elements.
1.2 Sources in the Environment, Environmental Transport and Distribution
Metallic vanadium does not occur in nature. Over 70
vanadium minerals are known, carnatite and vanadinite being the
most important from the point of view of mining. Production of
vanadium is linked with that of other metals such as iron,
uranium, titanium, and aluminium. As rich minerals rarely occur
in large deposits, ores with a low vanadium content, which exist
in large amounts, are important. Extraction of vanadium from
fossil fuels, including vanadium-rich oil and coal, tars,
bitumens, and asphaltites, is important in several countries.
During the first half of the 1980s, the global production of
vanadium (as vanadium pentoxide, V2O5) ranged from 34 to 45
million kg, China, Finland, South Africa, the USA, and the USSR
being the biggest producers.
Vanadium is mainly (75 - 85%) used in ferrous metallurgy as
an alloy additive in various types of steel. Its use in non-
ferrous metals is important for the atomic energy industry,
aircraft construction, and space technology. Vanadium is also
widely used as a catalyst in the chemical industry, where
vanadium pentoxide and metavanadates are especially important
for the production of sulfuric acid and plastics. Small
quantities of vanadium are used in a variety of other
applications.
From the point of view of environmental pollution, power-
and heat-producing plants using fossil fuels (petroleum, coal,
oil) cause the most widespread discharge of vanadium into the
environment. Burning of coal wastes or dumps of coal dust in
mining areas are other sources of vanadium discharge into the
atmosphere. In the distillation and purification of crude oil,
most of the vanadium remains in the residues. Burning of
distilled petroleum fuels contributes less vanadium to the
atmosphere.
Emissions of vanadium may be high in the vicinity of large
plants producing steel alloys. Vanadium is also released into
the air: during the re-smelting of scrap steel and the
transformation of titaniferrous and vanadic magnetite iron ores
into steel; from the roasting of vanadium slags; from vanadium
pentoxide smelting furnaces; and from electric furnaces in which
ferrovanadium is smelted.
Most of the vanadium that enters sea water is in suspension
or adsorbed on colloids. It does not react chemically with sea
water and passes mechanically through it. This is reflected in
its distribution on the sea bed in the form of silt. Only about
10% of the vanadium is present in a soluble form. The very low
concentrations of vanadium in sea water indicate that vanadium
is continuously removed from sea water, but the actual
mechanisms are largely unknown. Vanadium that accumulates in
ascidians, holothurians, and in marine algae will end up in the
silt.
1.3 Environmental Levels and Human Exposure
Concentrations of vanadium in ambient air vary considerably.
Elevated vanadium levels are believed to result from the burning
of fossil fuels with a high vanadium content. Thus, heating
requirements and seasonal differences in atmospheric inversions
are reflected by fluctuations in vanadium levels in air. Air
levels of vanadium can be reduced by using distilled instead of
residual fuel oil. In remote rural areas, levels are below
1 ng/m3, but burning of fossil fuels can exceptionally increase
local levels to about 75 ng/m3. Typical concentrations in urban
air vary over a wide range of about 0.25 - 300 ng/m3. Large
cities may have annual average air levels of the order of 20 -
100 ng/m3, with markedly higher concentrations during the winter
months compared with the summer months. In the vicinity of
metallurgical industries, concentrations of 1 µg/m3 are often
found. Assuming an average air concentration of about 50 ng/m3,
about 1 µg of vanadium may enter the respiratory tract daily.
Vanadium concentrations in drinking-water are generally less
than 10 µg/litre. A typical range is 1 - 30 µg/litre with an
average of about 5 µg/litre.
The main source of vanadium intake for the general
population is food. Reported vanadium concentrations in food
tended to be higher in early studies compared with more recent
measurements, which have shown concentrations in the range of
0.1 - 10 µg/kg wet weight, with typical concentrations of about
1 µg/kg. Recent estimates of daily intake suggest a range of
10 - 70 µg with the majority of estimates below 30 µg: higher
estimates of up to 2 mg suggested in earlier studies were most
likely due to analytical differences.
Exposure to high concentrations of vanadium in the air may
occur in working environments. In the production of vanadium
pentoxide, dust concentrations containing the pentoxide can
range from 0.1 to 30 mg/m3, and concentrations of about 0.5 -
5 mg/m3 are not uncommon in the production of vanadium metal and
vanadium catalysts. The highest vanadium concentrations in air
occur in boiler cleaning where dust concentrations of 50 -
100 mg/m3, but sometimes reaching 500 mg/m3, have been
encountered. Such dusts contain 5 - 17% of vanadium pentoxide
and 3 - 10% of lower oxides. These levels are not
representative of vanadium concentrations in the air in modern
plants, where levels are usually much lower.
1.4 Kinetics and Metabolism
The rate of pulmonary absorption of various vanadium
compounds has not been determined, but it has been estimated
that about 25% of soluble vanadium compounds may be absorbed.
The results of experimental animal studies have shown complete
clearance of the relatively soluble vanadium pentoxide from the
lung in 1 - 3 days following acute exposure. When 48VOCl3 was
instilled intratracheally in the rat lung, 50% was cleared
within the first day; 3% remained after 63 days.
Vanadium salts are poorly absorbed from the human gastro-
intestinal tract, only 0.1 - 1% of the very soluble oxytartaro-
vanadate being absorbed. A very low level of gastrointestinal
absorption has also been seen in animal studies, and, though it
has been shown that soluble vanadium compounds may be absorbed
through the skin of rabbits, the dermal absorption of vanadium
compounds is likely to be extremely small.
Absorbed vanadium is mainly transported in the plasma.
Vanadium concentrations in all tissues are generally low, but
are higher in the liver, kidney, and lung than in other tissues.
Levels in the liver may be in the range of 4.5 - 19 µg/kg wet
weight and those in kidney, 3 - 7 µg/kg. Higher levels may be
found in lung tissue with mean concentrations ranging from 10 to
130 µg/kg wet weight. Small amounts have been found in the
placenta, and vanadium passes through into the membranes rather
than the fetus. Vanadium is present in breast milk and saliva.
It also passes through the blood-brain barrier. Reported levels
in human blood differ widely, levels in whole blood and serum
lying within the range of 0.01 - 0.4 mg/litre. Most studies
have shown levels below 0.1 mg/litre.
Because of the low level of absorption in the gastro-
intestinal tract, ingested vanadium is mainly eliminated
unabsorbed with the faeces. The principal route of excretion of
absorbed vanadium is through the kidneys. Vanadium concentra-
tions in urine are of the order of 0.1 - 0.2 µg/litre. The
majority of studies on occupationally exposed populations have
shown a poor correlation between vanadium concentrations in air
and the amounts excreted in urine. However, in very highly
exposed workers, urine-vanadium levels increased 20 - 30 times
over a work-shift.
1.5 Effects on Experimental Animals and In Vitro Test Systems
Vanadium is an essential element for chicks and rats.
Vanadium deficiency in these species causes reduced growth,
impairment of reproduction, and disturbance of the lipid
metabolism. Vanadium has a diuretic and natriuretic action in
rats and inhibits the Na+-K+-ATPase (EC 3.6.1.3) in microsomal
fractions of kidney, brain, and heart of several species. The
observation of the inhibiting effects on Na+-K+-ATPase led to
the discovery that a variety of enzymes are vanadium sensitive.
For instance, ATP phosphohydrolase, ribonuclease, adenylate-
kinase, phosphofructokinase, and glucose-6-phosphatase are
inhibited by vanadium compounds.
In general, vanadium is better tolerated by small animals,
such as the rat and mouse, than by larger animals including
the rabbit and horse. The toxicity of vanadium is low when
administered orally, moderate when inhaled, and high when
injected. A 1-h LC50 of 70 mg/m3 has been reported for the
inhalation of vanadium pentoxide in the rat. The minimum
concentration of vanadium pentoxide that caused mild signs
of acute poisoning in the rat was 10 mg/m3 air. Exposure of
rabbits to vanadium pentoxide at 205 mg/m3 resulted in
conjunctivitis and tracheitis, pulmonary oedema,
bronchopneumonia, and death within 7 h. The exposure of rats
for 2 h every other day for 3 months to 3 - 5 mg/m3 caused
pathological changes only in the lungs. The endothelium was
swollen, there was capillary congestion, perivascular oedema,
and small haemorrhages indicating altered vascular permeability.
Similarly, respiratory symptoms, such as nasal discharge,
sneezing, dyspnoea, and asthmatic reactions, were seen in
rabbits exposed to vanadium trioxide aerosol at 40 - 75 mg/m3,
for 2 h/day over 9 - 12 months.
The effects of acute and long-term inhalation exposure on
the respiratory tract may partly be due to the effect of
vanadium on the macrophages. A 50% reduction in the viability
of cultured rabbit macrophages was seen after exposure to 13 µg
vanadium/ml (as vanadium pentoxide) for 20 h. Exposure for 2 h
(vanadium pentoxide) reduced the viability of murine pulmonary
alveolar macrophages at a dose of 7 µg vanadium/ml.
Vanadium pentoxide administered in the diet at 0.05 - 0.5 mg
vanadium/kg, per day, for 80 days, caused impairment of
conditioned reflexes in the rat. Daily parenteral injection of
sodium metavanadate (3.2 µg/kg body weight per day, for 10 - 15
days) increased the reactivity of cytochrome oxidase in guinea-
pig brain, whereas a dose of 128 µg/kg per day did not induce
any effects and 5.12 mg/kg body weight per day reduced the
activity. Cholinesterase activity in the rat brain was reduced
by the intraperitoneal administration of 1 - 10 mg vanadyl
sulfate/kg.
Fatty changes with partial cell necrosis of the liver
occurred in rats and rabbits exposed by inhalation to vanadium
pentoxide, trioxide, or trichloride (10 - 70 mg/kg, 2 h/day, for
9 - 12 months). Fatty changes in the liver of rats also
occurred after exposure to ammonium vanadate.
Vanadate has a diuretic and natriuretic effect on rat
kidneys, but not on those of the dog or cat. This effect is
thought to be due to the inhibition of Na+-K+-ATPase, which, in
turn, inhibits the tubular reabsorption. Fatty changes in the
myocardium of both the rat and rabbit were seen after long-term
inhalation of vanadium pentoxide, trioxide, or trichloride (10 -
70 mg/m3, 2 h/day, for 9 - 12 months). Perivascular swelling of
the myocardium was also seen.
Rats given metavanadate subcutaneously (0.85 mg/kg body
weight) showed shedding of spermatogenic epithelium.
Gonadotoxic effects were suggested by the absence of
fertilization of female rats by male rats that had been exposed
subcutaneously to vanadium at 0.85 mg/kg body weight. The same
dose administered to female rats on the fourth day of pregnancy
increased the mortality of embryos.
Parenteral administration of ammonium vanadate (intra-
peritoneal) to pregnant Syrian golden hamsters and of vanadium
pentoxide (subcutaneous and intravenous) to pregnant rats
resulted in increased numbers of fetal deaths and significantly
increased skeletal abnormalities. These studies indicate a
possible teratogenic effect of vanadium.
There are few data on the mutagenicity and carcinogenicity
of vanadium compounds and limited indications of the muta-
genicity of vanadium. In a rec assay with Bacillus subtilis,
testing DNA damaging capacity, three compounds (VOCl2, V2O5,
NH4VO3), gave mildly positive results, while results of tests in
Escherichia coli and Salmonella strains were mostly negative.
Bacterial assays have given conflicting results and no firm
conclusions can be drawn.
No information is available indicating a carcinogenic action
of vanadium.
1.6 Effects on Man
No data are available on the effects of vanadium deficiency
in man, and, though possible regulatory roles of vanadium have
been suggested, a daily dietary requirement of vanadium for man
has not been defined.
1.6.1 Local effects and dose-response relationships
There are comparatively few reports about the effects of
vanadium exposure on the skin. Eczematous dermatitis has been
reported in workers exposed to vanadium pentoxide, with dust
levels as low as 6.5 µg/m3.
Inhalation of vanadium pentoxide produces local irritation.
The exposure of 2 volunteers to 1 mg/m3 for 8 h resulted, 5 h
later, in coughing that lasted for 8 days. Inhalation of
0.2 mg/m3 by 5 volunteers resulted in similar symptoms, i.e.,
coughing that started a little later (20 h after exposure) and
lasted for 7 - 10 days. Similar irritation was noted in 2
volunteers exposed to 0.1 mg/m3 for 8 h. A dose-response
relationship was observed when 11 volunteers were exposed to
0.4 mg vanadium pentoxide/m3 condensation aerosol. Tickling and
itching with dryness of the mucous membranes of the mouth were
reported by 5 subjects at 0.16 mg/m3, whereas, at 0.08 mg/m3,
none of the subjects noted any effects.
Workers exposed to dust containing vanadium at 0.01 -
0.04 mg/m3, for about 10 months, showed irritant effects on the
mucous membranes of the upper respiratory tract. Cough,
increased production of sputum and irritation of the eyes, nose,
and throat occurred among workers exposed to a maximum of 0.9 -
5 mg vanadium/m3. At high exposures (dust concentrations
ranging between 5 and 150 mg/m3), workers developed atrophic
rhinitis, and chronic bronchitis. Blood-stained sputum,
haemoptysis, and bronchospasm were seen in a proportion of those
exposed. In workers exhibiting asthmatic reactions, when
exposed to vanadium pentoxide, there was no indication of
specific sensitization; the mechanism is thought to be a direct
chemical one.
Among the local effects caused by vanadium exposure, the
green tongue occurring in a proportion of the exposed is
considered a sign of exposure rather than a toxic effect.
1.6.2 Systemic effects and dose-response relationships
The effects of vanadium on dental caries is a debatable
issue. It has been claimed that, when added to the diet of
hamsters, vanadium had a favourable effect on dental caries. It
has also been shown, in one report, that the application of an
ammonium salt of vanadium reduced caries in children. However,
other studies between 1955 and 1968 failed to demonstrate such
beneficial effects of vanadium, and in one study, an increase in
caries was observed after administration of vanadium in the
drinking-water at 2 mg/litre.
The effects of vanadium on cholesterol levels have not been
fully elucidated. Studies in the 1950s and 1960s claimed a
temporary drop in cholesterol levels in patients fed ammonium
oxytartarovanadate and ammonium vanadyltartrate, for several
weeks, at 50 - 200 mg/day. Although some data on experimental
animals have indicated that vanadium reduces cholesterol levels,
this has not been convincingly shown in human beings.
The results of studies on the effects of vanadium pentoxide
on rats have shown a decrease in cysteine in hair and also a
reduction of co-enzyme A in the liver, which could explain the
mechanism behind the reduction of cysteine. Data on the effects
of vanadium on haematopoiesis are inconsistent, and it has not
been possible to assess the effects of low-level vanadium
exposure on iron metabolism. Vanadium has been shown to inhibit
the Na+-K+-ATPase (EC 3.6.1.3) in human red blood cells.
Systemic effects are rare in workers exposed to vanadium
compounds. Nonspecific signs and symptoms including headache,
weakness, nausea, vomiting, and ringing in the ears have been
reported, and there have been reports of dizziness or giddiness
and neuraesthenic and vegetative symptoms. A few early reports
mention tremor. It is not possible to derive dose-response
relationships for these effects on the nervous system. They are
likely to be associated only with fairly high exposure levels.
Systemic effects such as anaemia, leukopenia, and basophilic
granulation of leukocytes have been reported, but cannot be
expressed in relation to any particular exposure level.
Although fatty changes in the liver and kidney have been seen in
experimental animals, there are no data on human beings to
evaluate these effects.
In exposed workers, palpitations of the heart at rest and on
exercise have been reported. Transient coronary insufficiency
and a high incidence of extrasystoles have also been reported.
The association between these symptoms and vanadium is doubtful.
Low-level exposure of workers to vanadium pentoxide at 0.01 -
0.04 mg/m3 air for about 10 months, preceded by exposure to
0.2 - 0.5 mg/m3 for about 11 years, did not cause any
pathological effects on the blood picture, the cysteine level in
hair, or the respiratory function. Wheezing was more common in
exposed workers than in controls.
A few attempts to relate vanadium levels in ambient air to
adverse effects on the general population have been made.
Positive correlations between mortality from cardiovascular
disease, lung carcinoma, and bronchitis, and vanadium air
concentrations have been reported, but, so far, causal
associations have not been reported. Further studies on the
possible effects of vanadium exposure on the general population
are needed, with better control of confounding factors and
various intercorrelations than that in available studies.
1.7 Evaluation of Health Risks for Man
There is no convincing evidence that vanadium is an
essential element for man. Vanadium interferes with a multitude
of biochemical processes, and its physiological role should be
carefully assessed. Vanadium penetrates the blood-brain barrier
and is present in breast milk. Effects on the fetuses of rats
and hamsters when vanadium was administered to pregnant animals
indicate transfer across the placental barrier; however,
Vanadium appears to concentrate in the membranes rather than in
the fetus.
Current levels of vanadium in the ambient air have been
associated with mortality in the general population due to
various diseases of the heart and lung. All studies reporting
such relationships have had serious flaws, and no causal
relationships between vanadium and disease in the general
population have been established.
Practically all the information on adverse effects on human
beings has been derived from controlled, therapeutic, or
occupational exposure to concentrations that do not occur under
normal conditions. Exposed workers may suffer from irritation
of the eyes and the respiratory tract. There is a dose-response
relationship between the concentration of vanadium in air and
its irritant effects. With short-term inhalation exposure to
vanadium pentoxide at a concentration of about 0.1 mg/m3,
irritation is manifested as coughing with increased production
of mucous. Continuous exposure to even lower levels (0.01 -
0.04 mg/m3) may cause some irritation, but does not impair lung
function. A reversible decrease in forced vital capacity (FVC)
has been reported with exposure to a dust containing 15%
vanadium at a level of about 0.5 mg/m3. High exposure levels of
5 - 150 mg/m3 cause atrophic rhinitis and bronchitis with a risk
of bronchospastic effects. Eczematous dermatitis may occur with
low-level exposure to vanadium pentoxide (6.5 µg/m3).
Non-specific effects, such as headache, nausea, weakness,
ringing in the ears, and palpitation, have been reported in
exposed workers. These effects have not been related to any
specific exposure level, but, on such occasions, it has been in
the mg/m3 air range. Such symptoms may be taken as an
indication of the need for personal protection in work tasks
associated with the risk of heavy exposure to dusts containing
vanadium.
Several reported effects of vanadium need further research,
including the effects on cholesterol levels, iron metabolism,
and haematopoiesis. Available data do not imply any risk of
carcinogenic effects; however, the data cannot be considered
conclusive. There are only weak indications of possible
mutagenic effects of vanadium compounds. The results of studies
on point mutations in bacteria are conflicting, and there are
too few studies to draw definite conclusions with respect to
mutagenicity. The scanty evidence of spermato- and gonadotoxic
effects needs corroboration. The available data suggest that
vanadium may be embryotoxic and gonadotoxic. However, the
results indicating the induction of teratogenicity require
further confirmation.
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1 Identity
Vanadium (V) is a greyish ductile metal with an atomic
number of 23, an atomic mass of 50.942, a melting point of 1890
± 10 °C, a boiling point of 3380 °C at 1 atm (1.013 x 105 Pa),
and a specific gravity of 6.11 at 18.7 °C (Weast, 1986-87).
Vanadium has two natural isotopes, 50V and 51V, and several
radioactive isotopes (46-49V, 52-54V) have been obtained
artificially (Clark, 1975; Weast, 1987).
2.2 Physical and Chemical Properties
Vanadium has a maximum oxidation state of +5. Compounds of
vanadium may contain vanadium in oxidation states of -1, 0, +2,
+3, +4, and +5. Vanadium is usually found bound to oxygen as a
negatively charged polymeric oxyanion that tends to complex to
polarizable ligands, such as phosphorus and sulfur (Buckingham,
1973; Cotton & Wilkinson 1980).
Vanadium's ability to be either an electronegative or an
electropositive metal results in a great variety of chemical
compounds (vanadium is second only to carbon in the number of
chemical compounds). Physical properties of some important
compounds are shown in Table 1 (Weast, 1987).
Vanadium usually occurs in the pentavalent state.
Pentavalent vanadium is stable in aqueous solutions over a wide
range of pH.
The formation of isopoly and heteropoly compounds is most
characteristic of pentavalent vanadium in aqueous solutions.
The tendency of vanadium compounds to form V-0-V-0 linkages is
due to the electronegativity of vanadium and to electronic
hybridization (Zolotavin, 1954).
Vanadium pentoxide (V205), the most common commercial form
of vanadium, dissolves in water (8 g/litre) to give a pale
yellow acidic solution containing vanadium species that are
moderately strong oxidizing agents (Cotton & Wilkinson, 1962).
Vanadium5+ is reduced to vanadium4+ by relatively mild
reducing agents. The 4+ state is the most stable oxidation
state for vanadium. Nearly all of the complexes of vanadium4+
are derived from the vanadyl ion (VO2+). Most of these complexes
are anionic and a few are non-electrolytes. Vanadium in this
oxidation state forms a large number of five or six coordinate
complexes, such as vanadyl acetylacetonate and vanadyl
porphyrins found in crude petroleum.
Vanadium3+ (e.g., V203) is completely basic and dissolves in
acid to give the green hexa-aquo ion (V(H2O)6)3+. Vanadium3+ is
a strong reducing agent that slowly attacks water with the
liberation of hydrogen and the production of vanadium4+. The
hexa-aquo ion of vanadium is easily oxidized to vanadium4+.
Table 1. Physical properties of some vanadium compounds
--------------------------------------------------------------------
Compound Melting Boiling Solubility in water (g/litre)
point (°C) point (°C) Cold Hot
--------------------------------------------------------------------
Vanadiuma 690 1750 0.7b no data
pentoxide
Vanadiuma 1970 no data slightly soluble
trioxide soluble
Sodiuma 630 no data 211 388
metavanadate
Vanadium -28 ± 2 148.5 decomposes no data
tetrachloridea
Vanadium no data 127 decomposes no data
oxychloridea
Ammonium 200c no data 5.2 69.5c
vanadatea
--------------------------------------------------------------------
a From: Weast (1987).
b From: Cotton & Wilkinson (1980).
c Decomposes.
2.3 Analytical Methods
A review of analytical methods used to determine vanadium in
different media suggests that atomic absorption and
spectrophotometric assays are the most suitable for routine
analysis. Neutron activation analysis has been widely and
successfully used for the determination of vanadium in serum and
blood.
2.3.1 Atomic absorption analysis and emission spectrometry
Atomic absorption techniques have been most widely used for
the determination of vanadium in various media. Vanadium forms
heat-stable refractory oxides that are not completely
dissociated in a flame. The use of a high temperature
oxyacetylene flame improves the sensitivity of the method
(L'vov, 1970). Other ways of improving sensitivity have been
suggested (Christian & Feldman, 1970; Omang, 1971; Kragten,
1981; Wood et al., 1982). High sensitivity has been achieved
using flameless electrothermal AAS assays with a graphite
furnace. A flameless atomic absorption method using a graphite
furnace was recommended by NIOSH (1977) for the determination of
vanadium in air. A detection limit of 1 ng/ml for a maximum
sample injection of 100 µlitre was given, corresponding to an
absolute sensitivity of 0.1 ng of vanadium. A detection limit of
0.4 ng was reported by Hwang et al. (1972) using a flameless
atomic absorption method that was applicable to air, water, and
biological samples.
A method for the determination of vanadium in work-place air
using direct current plasma atomic emission spectrometry (DCP-
AES) was reported by Pyy et al. (1983). A detection limit for
vanadium in air of 0.004 mg/m3 and a practical working range of
0.01 - 100 mg/litre were suggested. The precision was given as
1%. The results of this assay correlated with those obtained
with both flame (FAAS) and electrothermal atomization (EIA-AAS)
atomic absorption spectrometry.
Vanadium and 11 other trace elements in natural water were
determined using AAS and the stabilized temperature platform
furnace. A detection limit of 0.6 µg/litre with a precision of
10 - 15% was achieved (Manning & Slavin, 1983).
Electrothermal AAS methods have been used to determine
vanadium in urine. Buchet et al. (1982) detected concentrations
in the range of 1 - 500 µg/litre, giving a coefficient of
variation for triplicate samples of less than 8% for 10 µg
vanadium/litre. A practical detection limit for vanadium in
urine of 2 µg/litre was reported by Pyy et al. (1984) also
using an electrothermal AAS method with a graphite furnace.
Extraction of vanadium with ammonium 1-pyrrolidine-
carbodithioate into 4-methylopentan-2-one reduced the detection
limit to 0.5 µg/litre.
Atomic absorption is widely used for the determination of
vanadium in biological materials, such as tissues and serum. A
detection limit of 30 pg and a sensitivity of 65 pg have been
reported using a flameless apparatus and graphite tubes (Stroop
et al., 1982).
AAS methods can also be used in the determination of
vanadium in other media such as crude petroleum (Wood et al.,
1982) and sewage sludge (Kempton et al., 1982). Improved
techniques have been developed (Barbooti & Jasim 1982; Slavin et
al., 1983) including the use of simultaneous AAS and mass
spectrometry (Styris & Kaye, 1982).
In general, emission spectral analysis has been considered
less accurate than colorimetric methods (Bagget & Huyck, 1959;
Sandell, 1959). However, it is a universal selective method by
which small amounts of vanadium can be determined in the
presence of numerous other elements. The relative sensitivity
of spectral analysis is 10-3 - 10-5%. Sensitivity can be
increased by prior separation of the element to be determined.
Inductively coupled plasma optical emission spectrometry has
been used for the simultaneous determination of several elements
in aerosol samples collected with cascade impactors (Broekaert
et al., 1982) and also for the determination of vanadium in
urine (Barnes et al., 1983).
2.3.2 Neutron activation analysis
Neutron activation analysis is more rapid and accurate than
other methods. Using this method, it has been possible to
determine up to 70 elements in amounts of 10-12 g in air (Dams
et al., 1970; Gershkovich & Stykan, 1972). In carrying out
neutron activation analysis, a weighted sample or test solution
is irradiated with a thermal neutron flux in an atomic reactor,
for a certain length of time (Flaherty & Eldrige, 1970; Frolov,
1970). During irradiation, one or several isotopes of the
element being tested are formed. The activity of the isotopes
formed is determined from the gamma peak by means of a
scintillation gamma spectrometer. The sensitivity of the method
depends on many factors including: size of the particle flux,
duration of sample irradiation, efficiency of the counter, time
elapsed since the beginning of irradiation, background response
of the counter, etc.
The chemical form of vanadium in water can be determined
using a 48V tracer and neutron activation (Orvini et al.,
1979).
Neutron activation determination of vanadium in biological
material is complicated by the high concentration of sodium,
even when a Ge/Li detector is used. Because of the short life
of the isotope, the sodium must be eliminated before
irradiation, normally by absorption on antimony pentoxide
(Ralston & Sato, 1971). Neutron activation has been
successfully used to determine vanadium in serum (Byrne & Kosta,
1978; Sabbioni et al., 1979; Cornelis et al., 1980, 1981) and
body tissues (Yukawa et al., 1980).
2.3.3 Spark-source mass spectrometry
Spark-source mass spectrometry is an excellent analytical
tool (Johnson et al., 1974). The absolute sensitivity of the
method is 10-11 - 10-12 g, and the relative sensitivity is
10-7 g-atom. Up to 70 elements can be recorded simultaneously
on the photographic plate and only a few milligrams of sample
are needed (Chupahin et al., 1972). This method is used for the
multi-element analysis of air and biological materials.
Evans & Morrison (1968) described the problems that occur in
analysing ashed biological material for vanadium using spark-
source mass spectrometry. The ash must be completely free of
organic mixtures, since vanadium belongs to the class of
elements in which inorganic compounds are completely bound to
biological material. The concentration of vanadium found by
spark-source mass spectrometry was 10 times as high as that
found by the spectral method in the same samples.
Vanadium levels in urine and biological tissues were
determined by Pilz & Komischke (1972) using salicylhydroxamic
acid. The vanadium complex was extracted with N-pentanol, and
the vanadium was determined in the extract by spectrophotometry.
Beer's law was observed, with concentrations of vanadium ranging
from 1 to 2000 µg/25 ml extract. There was no interference by
cobalt, nickel, zinc, molybdenum, tungsten, iron, calcium, lead,
or chromium.
2.3.4 Spectrophotometric analysis
Organic reagents are often used to improve the specificity
of spectrophotometric analysis. Over 80 organic reagents have
been suggested for the direct quantitative determination of
vanadium (Mustafin et al., 1969; Muzquin et al., 1981). The
specificity of the organic reagents can be increased when
complexing agents are used to bind the interfering ions. In
most cases, particularly those based on complexing reactions,
specificity and sensitivity are enhanced by prior separation of
vanadium, mostly by extraction. Acyl derivatives of
hydroxylamine containing the OC-NOH group show high selectivity
for pentavalent vanadium, when the product of interaction in a
highly acid medium is extracted (Tandon & Bhattacharya, 1961;
Majumdar & Das, 1965).
Spectrophotometric analysis based on catalytic reactions,
e.g., on acceleration of the oxidation of aromatic amines and
aminophenols with chlorates, bromates, periodates, and
persulfates in the presence of pentavalent vanadium compounds,
is widely used to determine trace amounts of vanadium (Bakal &
Liseckaja, 1971; Zheljazkova et al., 1972). The sensitivity of
kinetic methods is theoretically unlimited and their use for
analysing biological materials is quite promising, because of
the considerably reduced amounts of material needed for analysis
(Jacimirskij, 1967).
Welch & Allaway (1972) proposed a method to determine
nanogram quantities of vanadium by means of an acid oxidation
reaction catalysed by vanadium pentoxide. Christian (1971)
determined vanadium in blood and urine using a method based on
the catalytic effect of vanadium on the oxidation reaction of
phenylehydrazine-N-sulfonic acid with potassium chlorate.
Vanadium concentrations of 0.056 ± 0.033 mg/litre in blood-
plasma, 0.061 ± 0.019 mg/litre in red blood cells, and
0.022 ± 0.015 mg/litre in urine were detected using this
method.
2.3.5 Electrochemical methods
Vanadium is commonly determined by electrochemical methods,
namely by volumetric titration with electrometric detection,
such as potentiometry (Cassani, 1968), amperometry (Singh &
Sharma, 1970), as well as by coulometric titrations (Kostromin
et al., 1970), polarography (Shevchenko & Gorodynskij, 1964;
Budnikov & Medjantseva, 1973), and coulometry (Rigdon & Harrar,
1969). Catalytic reactions with polarographic, potentiometric,
and amperometric detection (Weisz et al., 1974) are also used.
Stripping voltammetry (Van den Berg & Huang Fi Qiang, 1984)
and other modifications of polarography (Veys, 1983), as well as
electrometric methods based on catalytic reactions are highly
sensitive but, depending on the composition of the sample, they
can involve operations to separate out interfering elements in
the sample. The selectivity of controlled potential coulometry
is high, making the separate determination of vanadium compounds
of different valencies possible. The introduction of
differential techniques into both coulometric titration and
controlled potential coulometry results in very high accuracy
(Agasyan et al., 1975; Shkolenok et al., 1977).
2.3.6 Chromatography
The chromatographic method has found little practical
application in determining trace quantities of vanadium though
Bonig & Heigener (1971) used selective paper chromatography to
determine microgram quantities of vanadium.
3. SOURCES IN THE ENVIRONMENT, ENVIRONMENTAL TRANSPORT AND DISTRIBUTION
3.1 Natural Occurrence
3.1.1 Rocks
Vanadium is a typical rare element, present in the earth's
crust at concentrations of around 0.015 g/kg, which is roughly
in the same proportions as chromium, strontium, and zirconium.
It is considerably more widespread than copper, lead, zinc, and
other minor elements. Some 70 vanadium minerals are known, of
which 40 are vanadates. The main vanadium minerals are
vanadinite (19% vanadium pentoxide), descloizite (220 g/kg),
cuprodescloizite (170 - 220 g/kg), carnotite (200 g/kg),
roscoelite (210 - 290 g/kg), and patronite (170 - 290 g/kg).
Admixtures are found in the ore minerals titaniferromagnetite
(up to 88 g vanadium pentoxide/kg), magnesioferrite (160 g/kg),
magnetite (6 g/kg), rutile (1 g/kg), and ilimenite (4 g/kg).
Metallic vanadium does not occur in nature, and the richer
minerals rarely occur in large deposits. Vanadium compounds are
present in fossil fuels (oil, coal, shale), and some oilfields
have a high vanadium content (NAS, 1974).
Vanadiferrous phosphorites (1 - 10 g/kg), asphaltites (up to
500 g/kg in ash), and titaniferrous magnetite placers, mainly of
the sea-beach type (about 3 g/kg), are important sources of
vanadium. Oolite brown iron ore (ferrophosphorous ore), which
contains only small amounts of vanadium pentoxide (0.7 - 2 g/kg)
but occurs extensively, carbonaceous cherts (15 - 20 g/kg),
bauxites (0.2 - 0.4 g/kg), the ash of coal and combustible shale
(2 g/kg), and ferromanganese nodules in the ocean, may all
provide sources for vanadium extraction (Todria, 1963; Holodov,
1968, Schumann-Vogt, 1969; Borisenko, 1973; Rose, 1973; NAS,
1974). The most important deposits of vanadium ores are found
in Canada, Finland, Namibia, South Africa, Sweden, the USA, the
USSR, and Zambia (Borisenko, 1973).
3.1.2 Soils
The vanadium contents of soils are related to those of the
parent rocks from which they are formed and range from 3 to 310
mg/kg, the highest concentrations being found in shales and
clays (Waters, 1977). Vanadium is evenly distributed in the
soil horizons, but there is sometimes a higher level in the A
horizon, possibly connected with the vital activity of plants.
In the neighbourhood of vanadium-bearing rocks or of large
amounts of iron oxides, a moderate local increase in soil-
vanadium levels may be found. Vanadium is present in the soils
of France, Japan, Spain, the United Kingdom, and the USA at
levels that are partly determined by the distribution of iron in
these soils (Holodov, 1968); levels ranged from 1 to 680 g/kg
(Vinogradov 1957). The lowest concentration was reported from
Japan, and the highest from Spain. Vinogradov (1957) found
lower vanadium concentrations in USSR podzols than in tundra and
chernozem soils.
3.1.3 Water
The levels of vanadium in fresh water in different parts of
the world vary from undetectable to 0.220 mg/litre (Table 2).
The geographical differences in fresh water vanadium levels are
due to differences in rainwater runoff from natural sources or
in industrial effluent. Data on vanadium levels in waters
contaminated with industrial effluent are presented in section
3.4.1. Some data on vanadium in sea-water are presented in
Table 3.
3.1.4 Air
Natural sources of airborne vanadium are marine aerosols and
continental dust. The concentration of vanadium in the air at
the South Pole is very low (0.001 - 0.002 ng/m3) (Zoller et al.,
1974). Levels in ocean air in the middle latitudes are about
two orders of magnitude higher (Hoffman et al., 1972; Martens et
al., 1973).
Atmospheric concentrations of vanadium from continental dust
and sea spray can be predicted using various models (NAS, 1974).
Concentrations of 0.1 ng/m3 (range, 0.02 - 0.8 ng/m3) measured
over the eastern Pacific Ocean and 0.72 ng/m3 (range, 0.21 - 1.9
ng/m3) over rural northwestern Canada agree with these
predictions, and can be regarded as natural background levels.
Many rural areas in the USA display similar or only slightly
higher levels. However, in northeastern USA, rural air
concentrations are higher, ranging from 2 to 64 ng/m3, and are
attributed to the local burning of fuel oil with a very high
vanadium content (section 4.1.1).
Only small amounts of airborne vanadium are produced as a
result of volcanic action (Zoller et al., 1973).
3.1.5 Plants
Vanadium occurs in small amounts in all plants, usually at
concentrations of a few mg/kg dry weight. Within a given
species, variation is influenced by soil-vanadium levels, soil
acidity, and growing conditions, but the range of variation is
not large. The vanadium concentrations in roots are nearly the
same as the level in the soil in which they are grown. Vanadium
levels are lowest in the aerial portions of most plants and are
unrelated to soil levels. Bertrand (1950) found vanadium in
each of 62 plant species analysed; mean concentrations in higher
plants were 0.16 mg/kg fresh weight, 1 mg/kg dry weight, and
7 mg/kg ash. A mean level of 1.2 mg/kg was found in the leaves
of woody plants by Hanna & Grant (1962).
Vanadium accumulation occurs in the fly agaric mushroom
(Amanita muscaria) , which contains about 100 times as much as
other mushrooms or plants (Bertrand, 1950). Cowgill (1973)
determined vanadium concentrations in fresh-water plants in the
range of 0.4 - 80 mg/kg. The higher value of 80 mg/kg was found
in the pickerel weed (Pontedaris cordata) , which is a probable
accumulator. Mosses (Hypnum cupressiforme) also accumulate
vanadium; concentrations of about 10 mg/kg have been measured in
rural mosses, whereas concentrations may be as high as 50 -
250 mg/kg in mosses from city areas (Tyler, 1970; Ruhling,
1971).
Table 2. Vanadium levels in fresh water
-----------------------------------------------------------------------------
Source of water Vanadium level Reference
-----------------------------------------------------------------------------
Japan
Rivers of Japan 0.001 mg/litre Sugawara et al. (1956)
Waters of 5 Japanese 0.0001-0.087 mg/litre Sugawara et al. (1956)
lakes (average, 0.0007
mg/litre)
USA
Rivers of Colorado 0.2 - 49.2 µg/litre Linstedt & Kruger (1969)
Rivers of New Mexico up to 19 µg/litre NAS (1974)
Rivers of the USA 0.001 mg/litre Durum & Haffty (1963)
Rivers of the Colorado to 70 µg/litre Schroeder (197Oa)
plateau
Wyoming River 30 - 220 mg/litre Schroeder (197Oa)
USSR
30 large rivers traces to 0.43 mg/litre Konovalov et al. (1968)
average 0.037 mg/litre;
average in dissolved
form, 0.0012 mg/litre
Protva and Tarusa 0.007-0.0135 mg/litre Tjurjukanov (1963)
Rivers
Moscow River 0.0025-0.0074 mg/litre Tjurjukanov (1963)
Rivers of the Klinsk- 0.005-0.0074 mg/litre Tjurjukanov (1963)
Dmitrovsk ridge
Waters of the area west 0 - 34 µg/litre Petuhov et al. (1969)
of the Kama River in the
Tartar ASSR: rivers and
lakes
Uzbek SSR: surface 0.0003 - 0.003% Mirzaeva (1965)
waters
-----------------------------------------------------------------------------
Table 3. Vanadium levels in Sea-watera
------------------------------------------------------------
Water Vanadium level Reference
(mg/litre)
------------------------------------------------------------
Sea-water 0.0005 (average) Vinogradov (1944)
Sea-water 0.0003 Sverdrup et al.
(1950)
Near the Japanese coast 0.001 - 0.002 Sugawara et al.
(1956)
Sea-water 0.002 Goldberg (1961)
Western Pacific 0.003 Sugawara et al.
(1956)
Sea-water 0.002 - 0.029 NAS (1974)
------------------------------------------------------------
a Modified from: Holodov (1968).
3.1.6 Animals
Vanadium appears to be present in all animals, but tissue
levels in most vertebrates (especially land mammals) are so low
that detection is difficult. Higher concentrations have been
found in marine species, especially invertebrates (Bertrand,
1950). In land mammals, the highest levels occur in the liver
and skeletal tissues.
Estimates by Vinogradov (1959) and Schroeder (197Oa) of
vanadium concentrations in animals are shown in Table 4.
Limited data for several tissues of wild animals are shown in
Table 5, and some concentrations in domestic animal tissues,
measured by sensitive methods, are given in Table 11 (section
4.1.3.1). On the whole, these agree with Bertrand's
observations.
Using neutron activation analysis, Fukai & Meinke (1962)
reported that concentrations of vanadium in the soft tissues of
fish were 1000 times those in seaweeds and molluscs. The
highest concentrations of vanadium in marine organisms have been
found in certain ascidians (sea squirts) (e.g., Phallusia
mamillata , 1900 mg/kg), certain holothurians (sea cucumbers)
(e.g., Sticopus mobii , 1200 mg/kg), a mollusc (Pleurobranchus
plumula , 150 mg/kg), and marine algae.
Table 4. Vanadium levels in animalsa
----------------------------------------------
Animal Vanadium concentration
(mg/kg dry weight)
----------------------------------------------
Coelenterate 2.3
Annelid 1.2
Mollusc 0.7
Echinoderm 1.9
Crustacean 0.4
Insect 0.15
Fish 0.14
Mammal 0.4
----------------------------------------------
a From: Vinogradov (1959) and Schroeder (197Oa).
Table 5. Vanadium levels in tissues of wild animalsa
--------------------------------------------------
Tissueb Number of Vanadium concentration
samples (mg/kg wet weight)
Mean Range
--------------------------------------------------
Kidney 4 0.94 0 - 2.07
Liver 4 0.25 0 - 0.94
Heart 4 1.16 0 - 3.40
Spleen 1 1.16
--------------------------------------------------
a From: Schroeder (197Oa).
b Beaver, deer, woodchuck, rabbit, muskrat, and fox.
In certain ascidians, trivalent vanadium is present as a
chromoprotein called haemovanadin together with sulfuric acid in
green cells termed vanodocytes; in other forms, the free
haemovanadin is present in plasma (Hudson, 1964).
3.2 Man-Made Sources
3.2.1 Production levels and processes
The annual production of vanadium (as vanadium pentoxide)
ing 1980-84 was between 34 and 46 million kg (Table 6). The
estimated world capacity up to 1990 is shown in Table 7.
Table 6. Production of vanadium by major producersa,b,c
--------------------------------------------------------
Country 1981 1982 1983 1984
--------------------------------------------------------
Australia 0.1 0 0 0
China, Peoples Republic of 4.5 4.5 4.5 1.8
Finland 5.2 4.8 5.0 4.5
Japan 0.7 0.7 0.8 0.9
Norway 0.9 0.4 0 0
USA 13.9 10.1 3.6 5.9
South Africa 21.0 19.6 14.5 20.4
--------------------------------------------------------
a From: Wentzel (1985).
b Production in millions of kg V2O5 equivalent.
c Data on production in the USSR are lacking. It is
probably about 10 000-15 000 tonnes.
Table 7. World vanadium capacitya,b
------------------------------------------------------------------
Country 1981 1982 1983 1984 1985 1990
------------------------------------------------------------------
Australia/New Zealand 0.4 1.6 0 0 0 3.6
China, People's Republic of 5.4 5.4 5.4 5.4 5.4 5.4
Finland 5.2 5.2 5.2 5.2 3.1 0
Japan 1.3 1.3 1.3 1.3 1.3 1.3
Norway 0.9 0.9 0 0 0 0
South Africa 28.4 28.4 27.2 27.2 27.2 29.5
USA 13.9 16.4 14.3 14.3 9.5 15.4
Venezuela 0 0 0 0 0 2.7
------------------------------------------------------------------
a From: Wentzel (1985).
b Capacity in millions of kg V2O5 equivalent.
The major producers of vanadium are China, Finland, South
Africa, the USA, and the USSR.
European countries, together with Japan and the USA, use 85%
of the total output.
3.2.1.1 Extraction from ores
The production of vanadium is closely linked with that of
other metals (particularly iron, but also uranium, titanium, and
aluminium). It is sometimes extracted from ores directly as a
vanadium-rich alloy (e.g., ferrovanadium).
3.2.1.2 Extraction from fossil fuels
Petroleum is a source of vanadium. A number of oilfields
have a high vanadium content; the vanadium level in vanadium-
rich oil ash amounts to as much as 600 - 700 g/kg (Holodov,
1968; Borisenko, 1973; Aleshin et al., 1974; NAS, 1974). For
this reason, vanadium is extracted from petroleum ash in some of
countries (e.g., Canada, Italy, USA).
All coals contain vanadium, concentrations in various
coalfields ranging from extremely low to 10 g/kg (in coal)
(e.g., Argentina, USSR) (Holodov, 1968, 1973; Borisenko, 1973;
NAS, 1974). Coal ash constitutes a supplementary source of
vanadium (up to 300 g/kg).
Tar sands (Canada), bitumens, and asphaltites (Argentina,
Peru, USA, USSR) are potential sources of vanadium. For
instance, burning bitumen from the Sadkinskoe deposit (USSR)
yielded an ash containing 43 - 66% vanadium pentoxide (Holodov,
1968, 1973).
3.2.1.3 Extraction from slag
In some countries, vanadium is extracted from slag resulting
from the metallurgical production of catalysts (Pilz &
Komischke, 1972; Rose, 1973) or the processing of vanadium
catalysts. The levels of vanadium pentoxide in slags obtained
from Bessemer converters of pig iron made from Kachkanar ores
(USSR) were 135 - 140 g/kg (Pastuhov & Tretjakov, 1959). Slag
obtained at a factory in South Africa contained a vanadium
pentoxide concentration of about 250 g/kg (NAS, 1974).
3.3 Consumption and Use
3.3.1 Metallurgy
Vanadium has important industrial uses, mainly in ferrous
metallurgy, where 75 - 85% of all vanadium produced is used as
an alloy additive in making special steels. Pure vanadium is
very seldom used as it reacts easily with oxygen, nitrogen, and
carbon at a relatively low temperature (300 °C).
To produce various high-resistance carbon steels, vanadium
is combined with chromium, nickel, manganese, boron, tungsten,
and other elements. The amount of vanadium in the steel ranges
from 0.3 to 51 g/kg (Goldshtejn, 1967; Grin et al., 1971).
Vanadium may be a component of structural steels used in
building, transport, engineering, and boiler-making and in tool
steels. It is added to steel in the form of either
ferrovanadium (an iron/vanadium alloy containing 400 - 800 g
vanadium/kg) or vanadium carbide. Vanadium is also a major
alloying element in high-strength titanium alloys. The amounts
of vanadium used in recent years in the ferrous metal industries
of four major consumer countries are listed Table 8.
Table 8. Use of vanadium in ferrous metallurgy (tonnes)a
---------------------------------------------------------------------
1964 1965 1966 1967 1968 1969 1970 1971 1972
---------------------------------------------------------------------
Canada 115 113 - - - 187 231 - -
France 209 239 225 340 342 539 518 402 409
United 600 600 600 500 600 800 800 600 500
Kingdom
USA - 3709 4180 3425 3997 4333 3667 3346 -
---------------------------------------------------------------------
a From: US Bureau of Mines (1974).
3.3.2 Other industries
The consumption of vanadium by branches of industry other
than metallurgy has increased, as can be seen from the values
given for the USA in Table 9.
Table 9. Use of vanadium in non-ferrous
USA industries (tonnes)a
-----------------------------------------
1965 1966 1967 1968 1969 1970 1971
-----------------------------------------
562 703 1325 988 1250 991 810
-----------------------------------------
a From: US Bureau of Mines (1974).
Alloys of vanadium with non-ferrous metals (aluminium,
titanium, copper, etc.) are widely used in the atomic energy
industry, aircraft construction, and space technology. Vanadium
disilicide is used in the production of high-temperature
refractory products (Kubasky, 1957). With regard to the
production of chemicals, vanadium oxides and vanadates have
important applications as catalysts in: the synthesis of
sulfuric acid; the oxidation of organic compounds; petroleum
cracking; purifying exhaust gases; and oxidizing ethanol. These
vanadium compounds are also used in producing glass of different
types and colours, organic ion exchangers, luminescent
compounds, ethylene-propylene synthetic rubber, thermistors, and
switching elements. The pentoxide and various other salts of
vanadium are used in preparing glazes and enamels for porcelain
and pottery, in producing lacquers and paints, and as
developers, sensitizers, and colouring agents in photography and
cinematography. Vanadium is also used as a mordant in the
dyeing and printing of cotton, particularly for fixing aniline
black on silk. Europium-activated yttrium vanadate is used in
colour television tubes. Vanadium hydride can be used as a
neutron moderator in atomic reactors. Soluble salts of
arsenous-vanadous acid have been used as fungicides and
insecticides. Vanadium slags are used in casting shops as a
moulding material to improve the quality of the casting surface
and to facilitate cleaning.
In most of these applications, the quantities of vanadium
used are small. Some recycling takes place (e.g., with
catalysts).
3.4 Environmental Pollution Resulting from Production, Use, and Waste Disposal
Fig. 1 shows the cycle of the various chemical processes
involved in the production and recovery of vanadium. Expansion
of the mining and processing of vanadiferrous materials, and of
the use of vanadium in metallurgical and other industries, and
the use of petroleum at power stations and in engineering, can
lead to increased pollution of the atmosphere and watercourses
with vanadium compounds. Pollution is mainly by the penta- and
trivalent oxides.
3.4.1 Metallurgy
The most important industry with respect to vanadium
pollution is the metallurgical industry, in which vanadium is
used to obtain steel alloys. Because of the relatively low
melting point of vanadium pentoxide (690 °C), its fumes may
enter the air, condense, and form an aerosol with particle
diameters of up to 2 µm (Roshchin, 1968). Obviously, these
processes may lead not only to contamination of the air in
industrial premises, but also to contamination of the outdoor
atmosphere (where an aerosol of vanadium pentoxide forms part of
the smoke emission). Vanadium pentoxide was found in 87% of all
air samples taken in the vicinity of large metallurgical plants,
in concentrations ranging from 0.98 to 1.49 µg/m3. Concentra-
tions in 11% of the samples exceeded 2 µg/m3 (Pazhynich,
1967).
The process of re-smelting steel scrap also leads to the
discharge of a vanadium-containing aerosol into the atmosphere.
In 1968, in the USA, 43.5 million tonnes of steel were produced
from the re-smelting of scrap in basic oxygen furnaces. The
emission factor was calculated to be 21 kg particulates per
tonne of steel produced and the degree of emission control 97%.
The aerosol discharged into the air during this process
contained a vanadium concentration of 0.02%. Based on these
figures, an estimated 6 tonnes of vanadium escaped into the
atmosphere (US EPA, 1977).
Ferrovanadium used for alloys in steelmaking is produced in
electric arc furnaces. The charge consists of scrap steel,
fused sodium metavanadate, and carbon with silicon, aluminium,
or a combination of the last two elements, as a reducing agent.
An estimated 131 tonnes of vanadium were discharged into the air
as a result of ferrovanadium production in the USA in 1968 (US
EPA, 1977).
Discharge into the atmosphere is greatest from furnaces
roasting vanadium slags, vanadium pentoxide smelting furnaces,
electric furnaces, crucibles in which ferrovanadium is melted,
and crushing equipment (US EPA, 1977).
Metallurgical slag may contain significant concentrations of
vanadium. When titaniferrous and vanadic magnetite iron ores
are converted into steel, the resulting slag contains vanadium
pentoxide concentrations of up to 250 g/kg (Dovgopol et al.,
1974; NAS, 1974). Vanadium is released into the atmosphere
during the loading, transporting, unloading, and crushing of
slag. The slag formed when iron is smelted contains
considerably less vanadium than converter slag. However, in
view of the considerable and increasing use of blast-furnace
slags as building-materials and in motorway construction, they
can be sources of environmental pollution. For example, in a
plant smelting vanadium-containing titaniferrous magnetite, the
losses of vanadium in slag represented 18% of the vanadium
content of the original raw material (Dovgopol et al., 1974).
The solid wastes formed as a result of roasting slag during
the production of technical vanadium pentoxide may be another
source of environmental pollution. In this process, an average
of 5.16 tonnes of solid waste containing 1.2% vanadium pentoxide
are formed for every tonne of vanadium pentoxide produced
(Kurmaev, 1974).
The liquid waste and wash water from metallurgical plants
often contain large amounts of vanadium, up to several hundred
milligrams per litre, measured as vanadium pentoxide. Kurmaev
(1974) detected vanadium at a level of 702.8 mg/litre in
effluent from a vanadium pentoxide plant. In a new
ferrovanadium plant, purified waste water contained 340 mg
vanadium pentoxide/litre (Kurmaev, 1974). Unpurified waste-
water discharge from a vanadium pentoxide plant into an open
watercourse produced a vanadium level in the watercourse of
2 mg/litre (Seljankina, 1961). Linstedt & Kruger (1969) found
the highest river concentrations of vanadium near uranium-
vanadium plants and the lowest in water samples taken upstream
from the industrial areas (Table 2) (section 3.1.3). In
studies by Shilina & Malakhov (1974), water samples taken from
the Moscow River below the city contained 6 times as much
vanadium as samples taken above the city (0.06 and
0.01 mg/litre, respectively).
The pickling of steel casts or steel articles can include
vanadium in the pickling mixture. Waste hydrochloric, nitric,
hydrofluoric, and sulfuric acids from a steel smelting plant
contained 0.02% vanadium. The solid residue on the bottom of
the acid vats contained 2.4 g vanadium/kg (hydrochloric acid
vat) and 1.6 g vanadium/kg (nitric and hydrofluoric acid vats)
(Kurmaev, 1974); vanadium in waste acid that is not properly
treated may be a source of water pollution.
3.4.2 Fossil fuel combustion
Industrial plants producing power and heat and operating on
petroleum, coal, and heavy oils are the most widespread source
of vanadium discharge into the environment. In 1969, as a
result of the combustion of fossil fuels (coal and oil), about
20 000 tonnes of vanadium were discharged into the air in the
USA (NAS, 1974). The estimated levels of emission from burning
coal in the USA for 1969 are shown in Table 10.
In a study of the vanadium discharged from coal burning in
six electric power generating stations, the total amount
discharged into the air in 1968 was 3760 tonnes. Where there
were no ash-trapping devices, 65% of the ash entered the
atmosphere. The degree of atmospheric dispersion of ash
particles depended on the original coalfield, the size of coal
used, the type of furnace, the combustion conditions, and the
presence and type of ash-trapping devices (NAS, 1974).
In a study of the metal aerosol content of waste gas
emissions from an oil-fired electric power station, it was
reported that the concentration of vanadium pentoxide (and
oxides of aluminium, chromium, iron, and manganese) was not
affected by the type of boiler or mode of operation. Comparison
of the metal content in the fuel oil and waste gases showed that
90% was released into the atmosphere (Sokolov, 1986). In the
USSR, there is a trend towards a reduction in the use of heavy
fuel oils in electric power stations.
Other possible sources of vanadium discharge into the air
are the burning of coal tips or dumps of coal dust in mining
areas, but data are not available.
All crude petroleum oils contain vanadium at levels ranging
from 1 to 400 g/tonne, depending on the oilfield (Holodov, 1968,
1973; Shah et al., 1970; Christian & Robinson, 1971; Nelson,
1973; NAS, 1974). In the distillation of crude oil, almost all
the vanadium remains in the high relative molecular mass
hydrocarbon fractions. The vanadium contents of heavy fuel oils
range widely from 1 to 200 g/tonne and are almost a thousand
times greater than those of petroleum distillates. Assuming
that 10% of the vanadium is precipitated inside the plant (flue
and ash trap) while 90% is discharged into the air, it has been
calculated that atmospheric emissions in the USA as a result of
heavy fuel oil combustion were about 14 100 - 21 800 tonnes in
1970 (Holodov, 1968, 1973; NAS, 1974). Similar percentages were
found by Sokolov (1986).
Table 10. Estimated emissions of vanadium resulting from coal
burning in the USA, 1969a
-------------------------------------------------------------------
Type and use Coal Vanadium Vanadium Control Vanadium
of coal (1000 in coal in fly of discharged
tonnes) (tonnes) ash fly into the
(tonnes) ash (%) air
(tonnes)
-------------------------------------------------------------------
Bituminous coal
Electric power 308 642 9254 6015 85 902
utilities
Manufacturing 93 248 2797 1818 60 727
Retail 12 665 380 247 50 124
deliveries
Coking 92 901 2787 - 100 0
Subtotal 507 276 15 218 8080 1753
Anthracite coal 9275 1159 753 50 377
Total 2130
-------------------------------------------------------------------
a From: NAS (1974).
Distilled petroleum fuels produced in the USA (gasoline,
kerosene, diesel fuel, home-heating oils) contain 0.05 mg
vanadium/kg (NAS, 1974). The distillation process used leaves
nearly all of the vanadium originally present in the residual
fractions. Analyses of the spent gases from petrol engines,
sampled directly at the exhaust outlet, showed vanadium
concentrations of 0.1 - 0.2 mg/kg, and exhaust gases of diesel
engines contained 10 - 15 mg vanadium/kg. Six to 12 mg/kg of
vanadium was found in soot collected from the edges of flues in
a small oil-fired power station (Pilz & Komischke, 1972).
The amount of vanadium in natural gas is less than
0.5 g/tonne, and almost no vanadium is released into the
atmosphere on combustion (NAS, 1974).
3.4.3 Agriculture
Vanadium has been used as a trace fertilizer applied at the
rate of 0.75 - 1 mg/kg soil (Peterburgskij & Tormasova, 1969).
This practice must lead to an increased level of vanadium in the
soil, but further information on agricultural use is not
available.
3.5 Transport and Transformation
3.5.1 Geochemical processes
Vanadium is involved in various geochemical processes
occurring in the earth's crust. There is extremely wide
dispersion of vanadium during the formation of volcanic rocks
and sporadic accumulation with the formation of vanadium
minerals as a result of postmagmatic processes. Like all trace
elements that accumulate in soils, vanadium migrates within the
soil itself and within the system: rock-water-soil-vegetation-
animals-man.
During geochemical processes in the soil and in weathering
and podzolization, vanadium is shifted from the A horizon to the
B horizon (Kovda et al., 1959). However, vanadium shifting does
not occur during weathering processes that do not involve
movement of sesquioxides.
Vanadium concentrations in rocks are linked to the pH of the
rocks (Borisenko, 1973). Neutral and acid rocks contain lower
vanadium concentrations than basic rocks, and acid rocks contain
lower concentrations than neutral rocks. In magma of various
types (the main carrier of vanadium), about 92% of all vanadium
occurs in basic rocks (basalts, gabbro, amphibolites, and
eclogites), and about 8% occurs in acid and neutral rocks. Less
than 1% of the total amount of vanadium is found in ultrabasic
alkaline rocks.
The main carriers of vanadium in the sedimentation process
are ferric hydroxides and solid bitumens. The great affinity
between the crystallochemical properties of V3+ and Fe3+ is of
vital importance for the diffusion of vanadium. There is
roughly 400 - 500 times more iron than vanadium in the earth's
crust. Thus, iron is a "solvent" of trivalent vanadium, and is
responsible for its diffusion in magmatic rocks. The bulk of
the ferromagnesian rock-forming minerals (and also titaniferrous
magnetite and magnetite itself) trap vanadium during the
crystallization of rocks, and, during endogenous processes,
vanadium is very closely linked with trivalent iron. In the
formation of igneous rocks, vanadium is preferentially
concentrated in those with a high iron content.
3.5.2 Biogeochemical processes
The accumulation of vanadium in soils and in all other
materials depends directly on its concentration in the soil-
forming rocks, the atmosphere, and the oceans of the world.
Migration, diffusion, and concentration of vanadium in the
biosphere takes place as a result of its extraction by living
organisms from water, from food of both vegetable and animal
origin, and from different types of rock during their
decomposition and the formation of soils.
3.5.2.1 Transport in, and removal from, water
In assessing the relative importance of the two ways in
which vanadium is transported in water, Konovalov et al. (1968)
and Holodov (1968) concluded that 87% is carried away by the
rivers in suspended form, and 13% in solution. The average
level of dissolved vanadium in the rivers of Japan and the USA
(Sugawara et al., 1956; Durum & Haffty, 1963) were the same as
that recorded by Konovalov et al. (1968), i.e., 0.001 mg/litre.
The bulk of vanadium enters sea-water in suspended form or
sorbed on colloids. It accumulates in recent deposits, passes
through watercourses mechanically, and does not react chemically
with sea-water. This peculiarity of vanadium transport is
reflected in its distribution on the sea-bed in the form of
silt.
The fate of vanadium that is dissolved in water is more
complex. As very large amounts of dissolved vanadium have been
carried out into the oceans throughout all geological periods,
vanadium levels in sea-water of about 60 mg/litre might be
expected; in fact, levels do not exceed 0.003 mg/litre
(Goldschmidt, 1938; NAS, 1974), indicating that vanadium is
continuously removed from sea-water. Krauskopf (1963) concluded
that the vanadium content of sea-water is not dependent on
solubility and that natural reagents remove vanadium from the
water. There are two possible pathways, namely sorption and
biochemical processes. The migratory qualities of vanadium are
poor. The content of vanadium in the earth's crust is 0.015 g/kg
(Vinogradov, 1959), and a mean content in river water is
0.001 mg/litre. Thus, very little vanadium is transported via
water. The bulk of vanadium is precipitated on to the seabed
and becomes bound to silts (Petkevich et al. 1967; Strahov,
1968). Levels of vanadium dissolved in sea-water amount to
0.001 - 0.003 mg/litre. The vanadium comes from the 10%
dissolved in river water and is continuously precipitated from
the water by ferric hydroxides and organic matter (Krauskopf,
1963).
Biochemical reactions play an important role in the
extraction of vanadium from sea-water and conversion into a
sediment (Vinogradov, 1937; Holodov, 1973). This is confirmed
by the link between the concentrations of vanadium and organic
substances in sedimentary rocks and silt. However, in practice,
it is extremely difficult to determine the part of the vanadium
that has been assimilated by organisms and the part that has
been sorbed by the decomposing mass of organic matter or
introduced in dissolved form.
An important role in the biogenic migration of vanadium is
played by live marine organisms and plants. The ascidians and
holothurians are noteworthy vanadium accumulators (Bertrand,
1950) (section 3.1.6). Some marine algae are also capable of
accumulating vanadium (Krauskopf 1963). When they die, these
organisms promote accumulation of vanadium in the silt.
Thus, vanadium dissolved in sea-water is continuously
removed either by sorption or biochemical processes. In the
first case, the main precipitant is hydrated ferric trioxide; in
the second, vanadium is accumulated by marine animals, plankton,
and, less commonly, algal and plant organic material.
3.5.2.2 Occurrence in hydrocarbons
The accumulation of vanadium in organic concentrators is
linked with its occurrence in hydrocarbons (petroleum, asphalts,
peats, bitumens, and coal). Vanadium may enter petroleum
together with organic matter or accumulate in already-formed
petroleum from underground waters and petroliferous strata.
Apparently, both processes occur in nature. Secondary
transformation of petroleum into asphalt is accompanied by a
proportionate increase in the concentrations of the tar-asphalt
component and the vanadium linked to it (Vernadskij, 1940).
3.5.2.3 Biospheric redox processes
Vanadium takes part in redox processes not only of a
geochemical nature but also in plants and animals. Pejve &
Ajzupiet (1974), studying the intracellular distribution of
metals in plants, showed that a considerable number, including
vanadium, were linked to complex lipid substances of
comparatively high stability that persisted, even after the
cells had died. These lipids persisted in soils and silts and
served as a source of metal in sedimentary rocks. In various
types of plants, the proportional relationship between the level
of iron and those of manganese, copper, titanium, nickel,
chromium, cobalt, and vanadium decreased in the course of
evolution, and was least significant in the leaves of flowering
plants.
In a number of soil organisms, such as Microcococus lacto-
lyticus, Thiobacillus terrooxidans, and Ferrobacillus thio-
oxidans, there was a link between iron and vanadium in bio-
chemical processes (Zajic, 1969).
3.5.2.4 Transport in air
Information on the local movement and deposition of airborne
vanadium is presented in section 4.1.1. Strahov (1947) and
Ronov (1964) concluded that the gaseous envelope of the earth is
not of significant importance in the transport of vanadium, but
a study by Duce & Hoffman (1976) documented some transport of
man-made airborne vanadium over ocean areas. The authors
estimated that about 10% of this material was deposited in the
ocean. In a study of trace metals in European glaciers,
Jaworowski et al. (1973) showed the presence of small amounts of
vanadium, apparently deposited from the air, which had increased
in recent decades.
4. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
4.1 General Population Exposure
4.1.1 Air
Natural sources of vanadium, such as continental dust and
marine aerosols, cause only low natural background levels of
vanadium in air. In remote areas, such as the South Pole, the
concentrations range from 0.001 to 0.002 ng/m3 (Zoller et al.,
1974), and in the eastern Pacific Ocean, from 0.02 to 0.8 ng/m3
(Hoffman et al., 1969). In rural areas in Canada, the United
Kingdom, and the USA, concentrations have been reported to range
from 0.2 to about 75 ng/m3, with annual averages frequently
below 1 ng/m3 (Rahm, 1971; Cawse & Peirson, 1972; US EPA, 1977).
In general, air levels of vanadium are higher in urban areas
than rural areas. Annual averages may often be in the range of
20 - 100 ng/m3, though, exceptionally, higher averages exceeding
200 - 300 ng/m3 have been recorded in large cities, and the
maximum 24-h average may exceed 1000 ng/m3 (US EPA, 1977). In
all surveys, there have been conspicuous geographical and
seasonal variations. High concentrations of vanadium in air
have been attributed to the local burning of fuel oil with a
high vanadium content. The uptake of vanadium fall-out by
mosses (Hypnum capressiforme and Bryum argenteum) in the
Stockholm area indicates that heating oil is a major source of
vanadium (Rühling, 1971). In this regard, Faoro & McMullen
(1977) presented some interesting data (Fig. 2). The values
shown, especially for the period prior to 1971, are typical of
cold-climate cities where high-vanadium heavy fuel oils are
extensively used. The marked seasonal variations are due to
alterations in heating requirements and seasonal differences in
atmospheric inversions. The marked decline after 1970 is due to
the introduction of low-sulfur fuels; reduction of sulfur in oil
results in a proportional reduction in the vanadium content. A
similar effect can be produced by changing from heavy to
distilled fuel oil, as noted in Boston by Barry et al. (1975),
where levels of airborne vanadium for comparable months in 1966
and 1972 were 1.07 and 0.114 µg/m3, respectively.
These data illustrate the importance of fossil fuels as
sources of vanadium in urban air. The patterns observed in
other areas are similar but less extreme in concentration and
fluctuation. Because of the variations in vanadium
concentrations in oil and coal, community levels will depend
mainly on the actual vanadium concentrations in the fuels used
and on meteorological factors.
Pollution of the air by industrial facilities may be less
than that by power stations and heating equipment. At a steel
plant in the USA in 1967, concentrations of vanadium ranged from
0.04 to 0.107 µg/m3 and averaged 0.072 µg/m3, corresponding to
the mean concentration over 13 Pennsylvania towns (also
0.072 µg/m3) (NAS, 1974). The following levels of vanadium
pentoxide were found by Pazhynich (1967) in the USSR in areas of
extensive metallurgical activity not connected with vanadium
production: in the years 1964-65: 1.49 µg/m3 at 150 m from the
source of discharge; 0.47 µg/m3 at 500 m; 1.35 µg/m3 at
1000 m; and 0.98 µg/m3 at 1500 m. Near a plant producing
technical vanadium pentoxide, Kurmaev (1974) detected the
following 24-h mean levels of vanadium pentoxide: 0.004 -
0.012 mg/m3 at 500 m from the source; 0.001 - 0.006 mg/m3 at
1000 m; and 0.001 - 0.004 mg/m3 at 2000 m. Seventy to 72% of
the particles were less than 2 µg in diameter.
Boyarkina et al. (1978) studied vanadium precipitation in
and around an industrial city, in winter, by measuring
concentrations in snow. In the central area, a concentration of
24 µg/litre was found, decreasing to 3.2 µg/litre at a
distance of 40 - 50 km.
4.1.2 Water
Natural background levels of vanadium in water have been
discussed in section 3.1.3, and levels in industrial effluent,
in section 3.4.1. Durfor & Becker (1963) included vanadium in
their analyses for trace elements in drinking-water supplies in
large cities in the USA. Of the samples analysed, 91% showed
less than 10 µg vanadium/litre; the maximum concentration was
70 µg/litre, and the average was about 4.3 µg/litre. Many of
the samples were negative. Twenty-six percent of 3676 tap water
samples from 34 areas in the USA contained vanadium at
concentrations ranging from 1.3 to 33 µg/litre with a mean of
4.85 µg/litre (Greathouse & Craun, 1979).
Hoffmann et al. (1972) published data from a regional well-
water survey in Poland. The average vanadium concentrations
were 0.06 - 6 µg/litre, with a maximum single value of
15 µg/litre. Bottled waters from mineral springs frequently
contained higher levels; Schlettwein-Gzell & Mommsen-Straub
(1973) reported a range of 4 - 290 µg/litre in bottled waters
from Switzerland.
Highly-mineralized waters in Argentina contained 0.3 -
10 µg vanadium/litre (Trelles et al., 1970). These concentra-
tions often occur in conjunction with high concentrations of
arsenic and/or fluorides.
4.1.3 Food
4.1.3.1 Individual foods
Information on the vanadium contents of human food is
sparse. Data from two studies (Myron et al., 1977; Byrne &
Kosta, 1978) are combined in Table 11 with those from an earlier
study using a similar method (Söremark, 1967). The results of
these studies agree reasonably well, but differ in some respects
from the results of earlier work, especially that of Schroeder
et al. (1963). The principal difference is that Schroeder noted
high vanadium concentrations in fats and oils, whereas low
concentrations were found in the more recent studies. Such a
difference may be accounted for by the use of different
analytical methods. Similar discrepancies have been encountered
in the study of other trace elements, i.e., lower concentrations
have been found using more recently developed methods.
The data presented in Table 11 show low levels of vanadium
in most elements of the human diet. There are also some
interesting differences among specific foods. Grains contain
higher levels of vanadium than fruits and vegetables. Levels in
oils and fats and beef and pork are low, but those in the liver
and kidneys of cows and pigs are higher. Higher levels are
found in both the flesh and internal organs of the chicken, and
levels in fish flesh are also high. Vanadium levels in milk and
eggs are low, and those in beer and wine are high. Myron et al.
(1977) pointed out that processing appears to raise levels in
food (e.g., white versus brown rice; cereal, flour, bread, and
gluten versus grain; peanut butter; bologna and bacon versus
pork). No explanation was given for the very high levels in
dill and parsley.
Table 11. Vanadium concentrations in foods (µg/kg)a
---------------------------------------------------------
Study 1 Study 2 Study 3
---------------------------------------------------------
Grains
Wheat 3.6
Flour 15, 40
Bread 11.20 10, 13
Gluten 33
Oats 3
Oatmeal 6
Corn 0.7
Cornmeal 2
Brown rice 1
White rice 21 12, 30
Barley 14 1.6
Cereal 93
Fruits
Apple 1.1 4 0.3
Pear 0 0.2
Banana 3 0.2
Orange 1
Cherry 0.4
Apricot 0.2
Peach 0.2
Strawberry 31.41 (dry)
Blueberry 1.6
Vegetables
Potato 0.8 1 1.2, 1.9
Radish 52 5 0.6
Carrot 0 1 2.3, 2.4
Beet 0
Garlic 0.6
Onion 0.6
Leek 0.3
Navy bean 14
Pea 0 7 0.4
Tomato 0.03 2 0.3
Cucumber 2.1
Squash 4
Brussels sprout 0.5
Cauliflower 0.08 1 0.9
Cabbage 2 0.3
Lettuce 21 4 1.0, 2.7
Table 11 (contd).
---------------------------------------------------------
Study 1 Study 2 Study 3
---------------------------------------------------------
Spinach 35
Parsley 790 1800 (dry)
Mushroom 50 - 2 000 (dry)
Dill 140 431
Meats
Beef 0 1 0.4 - 1.3
Beef liver 2.4, 10 6 7.3
Pork 0 1 0.6, 0.9
Pork liver 8.4
Pork kidney 8.5
Bacon 5
Bolgna 8
Chicken, white 22 1.7
Chicken, dark 12
Chicken liver 37, 38
Chicken kidney 18
Cod 28 7.2
Mackerel 2.6 3.5
Tuna 11 10, 3
Lobster 43 5
Scallop 22
Oils and fats
Margarine 4
Soybean oil 1
Corn oil 1 3
Pumpkin seed oil 0.2
Lard 2 0.2
Nuts
Hazel nut 3.7
Peanut butter 44
Dairy products
Milk 0 - 0.1 3 0.2, 0.2
Powdered milk 0 - 0.2 25
Chocolate milk 21
Butter 1
Egg white 0.3 - 1.8
Egg yolk 2.0 - 3.6
Beverages
Coffee 1.6
Tea 1.3 0.3
Cola 0.7 1.5
Beer 11 8.4
Wine 3.5 - 3.2
---------------------------------------------------------
a Study 1: Söremark (1967) (neutron activation analysis).
Study 2: Myron et al. (1977) (atomic absorption spectroscopy).
Study 3: Byrne & Kosta (1978) (neutron activation analysis).
4.1.3.2 Complete diets
Byrne & Kosta (1978) estimated the daily intake of vanadium
to be "a few tens of micrograms," but added that it may vary
considerably. Assuming a very low rate of intestinal absorption
of vanadium in man (section 5.1.2), Byrne & Kosta calculated
intakes for 3 adults in whom they measured dietary
concentrations. The calculated intakes were 36, 66, and
11 µg/day, respectively.
Analyses of 9 selected hospital diets (Myron et al., 1978)
are given in Table 12. Each meal was prepared and analysed
separately by atomic absorption spectroscopy. The results were
similar to concentrations found in individual foodstuffs in
other studies given above. In a later study, Byrne & Kosta
(1979) reported on the determination of vanadium in total diet
samples obtained during a nutrition survey in 5 Italian towns
(Table 13). The concentrations agree with those reported by
Myron et al. (1978).
Table 12. Daily vanadium intake in dieta
------------------------------------------------------
Diet type (µg/day) (µg/g) (µg/1000
cal)
------------------------------------------------------
General-1 13.6 0.019 4.7
Cholesterol reducing-1 25.6 0.034 8.8
Cholesterol reducing-2 16.8 0.022 5.8
Cholesterol raising 30.1 0.046 10.5
General-2 28.0 0.040 9.8
Low calorie 12.4 0.029 10.6
Low salt 15.5 0.028 9.1
Puree 26.0 0.050 14.1
Soft 15.8 0.024 6.4
------------------------------------------------------
a Adapted from: Myron et al. (1978).
4.2 Occupational Exposure
In terms of occupational exposure, the most important
vanadium compounds are vanadium pentoxide, vanadium trioxide,
ferrovanadium, vanadium carbide, and vanadium salts, such as
sodium and ammonium vanadate. The oxides and salts are commonly
used in industry in powder form, giving rise to the possibility
of dust and aerosol formation, when the substances are crushed
or ground. Many metallurgical processes involve the production
of vapour containing vanadium pentoxide, which condenses to form
respirable aerosols. Boiler-cleaning operations generate dusts
containing the pentoxide and trioxide compounds. Combustion of
residual fuels with a high vanadium content is likely to produce
aerosols of the pentoxide as well as oxide complexes of vanadium
with other metals.
Table 13. Vanadium contents of Italian freeze-dried
total diet samplesa
--------------------------------------------------------
Town Dry Vanadium Daily
weight concentrationb vanadium
(g) (ng/g) intake (µg)
--------------------------------------------------------
Aosta 310 32.1 0.9 (2) 10.0
L'Aquila 173 46.0 3.4 (2) 8.0
Montfalcone 278 39.7 4.1 (2) 11.0
Mt. Amiata 377 29.7 0.8 (2) 11.2
Rome 285 42.3 4.6 (4) 12.0
Mean values 38.0 6.9 10.4 1.5
--------------------------------------------------------
a From: Byrne & Kosta (1979).
b Average and standard deviation; number of aliquots
in parentheses.
4.2.1 Metallurgy
The processing of metals containing vanadium includes
chemical treatment and high-temperature operations. However,
only moderate concentrations of vanadium were found in the
breathing zone of workers engaged in operations that would be
expected to produce the greatest fume exposure. During the
addition of vanadium to furnaces, concentrations ranged from
0.006 to 0.08 mg/m3 and, during tapping, from 0.004 to
0.02 mg/m3. Concentrations found in oxyacetylene cutting ranged
from 0.008 to 0.015 mg/m3 and, in arc-welding, from 0.002 to
0.006 mg/m3 (NAS, 1974).
Vanadium levels in metallurgical plants have been studied in
detail (Roshchin, 1968). Vanadium slag contains about 11 - 13%,
mainly in the form of trioxides of vanadium (measured as
vanadium pentoxide). Slags are used for the production of
vanadium pentoxide and ferrovanadium, and the process is
accompanied by extensive formation of iron oxide aerosol. Air
concentrations of the dust (mainly vanadium trioxide) found in
the main working positions (converter operator, mixer, and crane
driver) ranged from 20 to 55 mg/m3. Measured as vanadium
pentoxide, the contents of the swirling dust did not exceed
0.17 mg/m3. About 75% of the dust particles had a diameter of
less than 2 µm and 20% had a diameter of between 2 µm and
4 µm.
Breaking, loading and unloading, crushing and grinding, and
magnetic separation of vanadium slag causes thick dust
formation, with concentrations ranging from 30 to 120 mg/m3.
The slag contains 111 - 129 g vanadium pentoxide/kg. A diameter
of less than 2 µm was recorded for 70 - 72% of the particles;
86 - 96% had a diameter of less than 5 µm. When the slag is
roasted, free vanadium pentoxide is discharged into the work-
place air; atmospheric concentrations in the vicinity of
furnaces ranged from 0.04 to 1.56 mg/m3. During leaching and
precipitation, concentrations of vanadium in the air may be
high, sometimes exceeding 0.5 mg/m3.
The smelting and granulation of technical vanadium pentoxide
are accompanied by the formation of an aerosol. This aerosol
escapes when the product is poured for granulation. During the
loading of smelting furnaces, concentrations of vanadium
pentoxide ranged from 0.15 to 0.80 mg/m3. During smelting and
granulation, concentrations ranged from 0.7 to 11.7 mg/m3. In
other parts of the work-place, concentrations may range from
0.03 to 0.2 mg/m3.
In aluminium production, when bauxite is being converted
into alumina, the aluminate solutions accumulate vanadium salts,
which crystallize and precipitate out. Precipitated sodium
polyvanadate is smelted to form vanadium pentoxide, which is
cooled and settles in the form of thin plates. Vanadium
pentoxide dust (concentrations of up to 2.3 mg/m3) is given off
only in the terminal phase during tapping of the liquid product,
packing, and loading.
During the drying, sieving, and calcination of ammonium
vanadate and during the crushing, unloading, and packaging of
pure vanadium pentoxide, dusts are formed. When vanadium
pentoxide is sieved after calcination, the concentration in air
may range from 2.2 to 26 mg/m3. In plants with less
mechanization, incomplete sealing of equipment, and inefficient
local exhaust ventilation, concentrations of dust during these
operations ranged from 4.9 to 48.9 mg/m3.
In the production of ferrovanadium, there is a continuous
source of discharge of vanadium pentoxide and lower oxides
during the smelting process. Data on vanadium in air at various
sites are shown in Table 14.
Using spectrophotometric techniques, Roshchin (1968),
Katayeva & Sapunov (1974) and Kazimov (1977) found high
concentrations of vanadium during smelting and granulation
(range, 0.16 - 1.89 mg/m3; mean, 0.59 mg/m3; 104 samples),
production of ferrovanadium (range, 0.58 - 4.81 mg/m3; mean,
1.7 mg/m3; 110 samples), and roasting of the charge (range,
0.44 - 3.64 mg/m3; mean, 1.52 mg/m3; 112 samples).
Table 14. Vanadium levels in the air of a ferrovanadium planta
--------------------------------------------------------------------
Work-place/operations Vanadium pentoxide Lower oxides of
(mg/m3) vanadium (mg/m3)
--------------------------------------------------------------------
Work area of smelters and 0.1 - 2.6 0.05 - 1.2
helpers
Unloading of vanadium pent- 2 - 124.6
oxide from the bin and
charging of electric furnace
Crane driver's cabin during 0.07 - 9.43 0.03 - 0.1
smelting
Cutting up ferrovanadium 0.97 - 12.6
Maintenance of the furnace 7.5 - 30
--------------------------------------------------------------------
a From: Roshchin (1968).
Using high-volume sampling and atomic absorption analysis,
Usutani et al. (1979) measured vanadium pentoxide
concentrations in the air at several places in a vanadium
refinery. The highest concentrations (higher than 1 mg/m3) were
detected in samples collected during the removal of the vanadium
pentoxide flake. High-volume samples from other locations as
well as low-volume samples obtained over 6.5-h work shifts
showed lower concentrations (0.002 - 0.735 mg/m3).
When ductile vanadium is produced by the aluminothermic
process (based on the reduction of pure vanadium pentoxide with
aluminium powder), the violent exothermic reaction leads to the
release of a condensation aerosol of vanadium pentoxide. During
preparation of the charge mixture, work-place concentrations of
vanadium pentoxide ranged from 19 to 25.1 mg/m3. When the
burden was placed in crucibles inside the smelting chambers,
concentrations ranged from 64 to 240 mg/m3. During smelting,
concentrations at the operators' workplaces ranged from 0.17 to
0.6 mg/m3. Twenty to 30 min after smelting, levels declined to
0 -0.3 mg/m3. Ninety-eight percent of the condensation aerosol
particles produced had a diameter of less than 5 µm, and 82%
had a diameter of less than 2 µm (Roshchin, 1968).
In the production of vanadium by the vacuum carbon thermic
method, most of the pollution occurs during operations with
vanadium trioxide (Roshchin, 1968). Mixing of vanadium trioxide
in a closed mixer led to air concentrations in the workplace of
from 0.019 to 0.58 mg/m3. Unloading of the charge resulted in
high concentrations of 14.7 - 29.4 mg/m3. In the packing
department, when the charge was sifted in a fume cupboard,
concentrations in the breathing zone ranged from 0.58 to
4.7 mg/m3. When the charge was being weighed out and packed in
a fume cupboard, concentrations ranged from 3.38 to 6.76 mg/m3.
Levels of vanadium-containing dust and vanadium pentoxide in
the air during catalyst production are shown in Table 15.
Table 15. Air contamination in vanadium catalyst productiona
-----------------------------------------------------------------------------
Operation Dust (mg/m3) Vanadium pentoxide (mg/m3)
Minimum Maximum Most Minimum Maximum Most
frequent frequent
-----------------------------------------------------------------------------
Grinding and un- 5 45 7 - 9 1 7 1.5 - 3
loading vanadium
pentoxide
Loading ground 12 53 14 - 17 3.2 7.5 4 - 4.2
pentoxide into
the bin
Sifting and pack- 5 17.5 5 - 7 0.1 1 0.4 - 0.5
ing granules of
bulk contact
substance
-----------------------------------------------------------------------------
a From: Roshchin (1968).
4.2.2 Cleaning of oil-fired boilers
Significant occupational exposure to vanadium occurs during
the cleaning of boilers in oil-fired heating and power plants
and ships (Symanski, 1939; Roshchin, 1968; Kuzelova et al.,
1977; Levy et al., 1984). Fuel oil combustion results in the
formation of vanadium-containing dust, and large amounts of dust
result from operations connected with removing ash encrustations
in boiler cleaning and in cleaning the blades of gas turbines.
Most of these operations are carried out by hand, and the dust
in the air inside the boilers may range from 20 to 400 mg/m3,
the most common range being 50 - 100 mg/m3, with the dust
containing 5 - 17% vanadium pentoxide and from 3 to 10% of the
lower vanadium oxides (Roshchin, 1968). Kuzelova et al. (1977)
reported dust concentrations of 136 - 36 036 ml/m3 in the air
with vanadium concentrations ranging between 1.7 and 18.4
mg/m3.
Williams (1952) published air sampling data on boiler-
cleaning operations in the British power industry. He found
concentrations of soot dust at different points ranging from 239
to 659 mg/m3. The vanadium concentrations in the dust of the
superheater chamber was 40.2 mg/m3, while, in the combustion
chamber, the concentration was 58.6 mg/m3. Most (93.6%) of the
dust particles had a diameter of between 0.15 and 1 µm.
4.2.3 Occupational exposure limits
Some national occupational exposure limits for vanadium in
work-place air are shown in Table 16.
Table 16. Examples of occupational exposure limits for vanadium in various countries
---------------------------------------------------------------------------------------------------------
Country Legal status Exposure limit description Value Source
(mg/m3)
---------------------------------------------------------------------------------------------------------
Australia Recommendation Time-weighted average (TWA) (fume)a 0.05 ILO (1980)
Belgium Recommendation Time-weighted average (TWA) (fume) 0.05 ILO (1980)
Czechoslovakia Regulatory requirement Maximum allowable concentration (MAC) Hygienic Regula-
- Time-weighted average (TWA) 0.1 tions of the
- Ceiling value (fume) 0.3 Ministry of Health
- Ceiling value (dust) 1.5 of CSR (1985) (58)
(Regulation No. 7;
section 24/ZB)
Finland Regulatory requirement Maximum allowable concentration (MAC)a<