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OCR for page 510
Titanium
Titanium (Ti) is a dark, gray metal that ranks eighth in abundance in
igneous rocks. The concentration in the earth's crust is estimated to be
0.43 percent. The most important titanium ores are ilmenite (PeTiO3)
and rutile (TROD. Titanium is also found as a silicate (sphere), as
calcium titanate (CaTiO3), and in association with hematite deposits
(Browning, 19691. Titanium forms compounds in which it has an oxida-
tion state of +2, +3, or +4. It is used as a constituent of aluminum, tin,
and vanadium alloys and is particularly important as ferrotitanium in
the steel industry. Titanium oxide is used as a white pigment in paint
and as a constituent of the coating of welding rods. Titanium dioxide is
used as an ingredient marker in comminuted meats. Titanium com-
pounds are used as a mordant in the dyeing industry, as a constituent
of glass and ceramics, in surgical devices for properties of lightness and
tensile strength, and with carbon and tungsten in the manufacture of
electrodes and lamp f~larnents. Cobalt cemented carbides (Carbaloy)
used in cutting tools contain titanium, and the military uses titanium
chloride as a smoke screen.
ESSENTIALITY
No essential metabolic function for titanium has been established in
either plants or animals.
510
OCR for page 511
Titanium
METABOLISM
511
Published evidence on absorption of titanium from the alimentary tract
is contradictory. Lehmann and Herget (1927) found no evidence of
absorption when titanium oxide was fed. However, when Lloyd et al.
(1955) attempted to use titanium oxide as an indigestible marker for
digestion studies, they were unable to completely recover the element
In the feces. They suggested that prolonged retention in some portion
of the digestive tract (such as the cecum) may provide the explanation.
However, Tipton et al. (1966) found significant urinary excretion of
titanium in two humans consuming 0.37 and 0.41 mg per day in their
diet. Both individuals were in negative titanium balance, and about
equal amounts were found in feces and urine. It was not established
whether urinary titanium was derived from titanium absorbed during
the study or whether it came from previously established tissue stores.
SOURCES
The titanium concentration of herbage can be used as an index of soil
contamination (Barlow e' al., 1960), because soil concentrations of
titanium are about 10,000 times greater than those in uncontaminated
herbage (Swaine, 19551. A variety of plants were assayed by Bertrand
and Varonca-Sp~rt (1929a,b), who found titanium levels ranged from 0.1
to 5 ppm (dry basis) with a majority near 1 ppm. Mitchell (1957) found
a mean of 1.8 ppm (range 0.7-3.8) on a dry basis in red clover and a
mean of 2.0 ppm (range 0.9- 4.6) In ryegrass. Titanium concentrations
of individual human foods have not been reported, but Tipton et al.
(1966) reported the Away mean total diet titanium intakes of two
individuals were 0.37 and 0.41 mg per day.
The primary titanium exposures In industry are to the metal, the
dioxide, and the chloride. There seems to be general agreement that
titanium and its compounds are low In toxicity (Browning, 1969~.
However, since the powders of titanium are pyrophor~c and its liquid
form burns in air, several explosions have resulted from careless
handling. Hydrolysis of titanium chloride will result in release of
hydrochloric acid and a consequent hazard from exposure to that
chemical. It has been proposed that air titanium concentrations be
limited to 15 mg/m3 (Hamilton and Hardy, 1974~.
OCR for page 512
512 MINERAL TOLERANCE OF DOMESTIC ANIMALS
TOXICOSIS
It is questionable whether a specific toxicity of titanium has been
demonstrated. Ereaux (1955) stated that oral administration of large
amounts of titanium salts in the diet of experimental animals had no
adverse effect. Vernetti-Blina (1928) administered titanium oxide by
mouth, by subcutaneous injection, and by inhalation in varying dosages
over periods of 1 to 2 months. He concluded this compound was basic-
ally inert and innocuous. Even inhalation of the dust for ~ hours a day
for 30 days produced no significant clinical illness. At necropsy the
peribronchial glands showed some hyperplasia, and the lungs had an
increased amount of connective tissue in the stroma, with an exudate
in the large and medium bronchi (evidence only of the irritating effect
of the dust). Christie et al. (1963) exposed rats to titanium dioxide by
inhalation for up to 13 months. There was little tissue reaction, but lung
ash contained more than 10 percent titanium. Stokinger (1963) reported
that inhalation exposure to high levels of titanium chloride produced
severe respiratory distress, while lower levels (mean of 8.4 ppm) pro-
duced silicosislike lesions. When Bloom and Swensson (1958) injected
titanium dioxide intravenously, there was a decrease in circulating
thrombocytes. Implantation of small titanium discs into the abdominal
muscle of dogs for several months caused no irritation (Beder and
Eade, 1956~. Titanium plates and screws have also been used in fixation
of fractures in dogs and have proved inert (Beder et al., 1957; Gross and
Gold, 1957).
Ereaux (1955) has found topical application of titanium salicylate,
peroxide, tannate, and oxides beneficial for skin disorders. Kato and
Gozsy (1955) suggested that the therapeutic value of organic salts is due
to their stimulation of phagocytic activity of capillary endothelial cells,
thus increasing defense mechanisms of the skin without causing irrita-
tion. Deribere (1941) found titanium oxides were harmless when used
in cosmetics.
Industrial exposure of humans to titanium dust is generally believed
not to induce lung fibrosis (Vernetti-Blina, 1928; Lundgren and Ohman,
1954; Moschinski et al., 1959~. Inhalation of fumes of titanic acid and
titanic oxychloride resulted in marked congestion of the mucous
membranes of the pharynx, vocal cords, and trachea; followed by
cicatrization and stenosis of the larynx, trachea, and upper bronchi
(Heimendinger and Klotz, 1956~.
OCR for page 513
Titanium
TISSUE LEVELS
513
Tipton and Cook (1963) reported that most of the soft tissues of the
adult human body contain 0.1 to 0.2 ppm titanium (on a wet basis).
However, lungs averaged over 4 ppm, with some samples over 50 ppm.
Hamilton et al. (1972/1973) found the following mean titanium concen-
trations (parts per million, wet weight) in human tissues: muscle, 0.2;
brain, 0.8; kidney cortex, 1.3; kidney medulla, 1.2; liver, 1.3; and lung,
3.7. Losee et al. (1973) also found considerable variability in titanium
concentration of 29' samples of human dental enamel. Levels ranged
from 0.1 to 4.8 ppm (dry basis), with a mean of 0.46.
MAXIMUM TOLERABLE LEVEL
No evidence of oral toxicosis has been found.
SUMMARY
Titanium is a dark, gray metal that is found in the earth's crust at a
concentration of about 0.43 percent. It is used in alloys with aluminum,
tin, and vanadium and as ferrotitanium in steel. Its compounds are
useful as ingredient markers in comminuted meat, as pigments in paint,
in the coating of welding rods, in glass and ceramics, in implantable
surgical devices, and in electrodes and lamp filaments. Titanium has no
known metabolic function in plants or animals, and the metal and its
compounds appear to have low toxicity. Implantation of titanium metal
during the surgical repair of tissues produces no tissue reaction, and for
this reason (plus properties of lightness and tensile strength) titanium
has found considerable application in medicine.
OCR for page 514
1
S14 MINERAL TOLERANCE OF DOMESTIC ANIMALS
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Representative terms from entire chapter:
titanium oxide
