Titanium - Toxicology of Metals - page 841

The most common oxidation states are +4 (TiO 2 ) and
+3 (titanous, Ti 2 O 3 ); compounds having oxidation state
+2 (TiO) are less stable, as are oxycompounds such as
titanyl chloride (TiOCl 2 ). A number of organometallic
compounds of titanium, such as titanocene, are known;
the most common are the alkyl- and aryltitanates of
the general formula Ti(OR) 4 . Complex titanium com-
pounds possessing organic ligands are also known.
Titanium metal displays excellent corrosion resist-
ance: it is as resistant as platinum against many agents,
including concentrated nitric acid, moist chlorine gas,
and common salt solution. An important property of
titanium is that, on exposure to air or various liquids,
it rapidly develops a layer of oxide, which reduces its
reactivity (Kasemo, 1983). No metal or alloy is, how-
ever, completely inert in vivo . Elevated titanium con-
centrations have been reported in the blood, urine, and
nails of humans having titanium-containing implants
(Berglund and Carlmark, 1999; Bianco et al ., 1996). Tita-
nium dioxide exists in three crystalline forms: anatase,
brookite, and rutile (WHO, 1982). Titanium tetrachlo-
ride occurs as a colorless to light-yellow liquid that
is soluble in water but decomposes in hot water (US
Department of Health and Human Sciences, 1993).

g/m 3 at a sensitivity of 0.01 g/m 3 (Kalbasi

0.011 µ µ

et al ., 1995).
Neutron activation analysis has been used for the
determination of titanium in air, whereas spark source
mass spectrography has been used for the analysis of
water, food, and biological samples. The gravimetric
fi lter weight (G/FW) is the most common method
used for determining titanium and titanium dioxide
as particulate matter in air (NIOSH, 1980; 1994b,c);
spectroscopic methods are most commonly used for
detecting the metal associated with particulates in air
(NIOSH, 1994d).

3 PRODUCTION AND USES

3.1 Production
Titanium is one of the most common components in
the earth's crust (ninth in abundance, 0.6% by mass);
it occurs in a number of minerals as well as in liv-
ing systems and natural bodies of water. Among the
various mined titanium minerals, ilmenite is of great
commercial signifi cance. The world production of
ilmenite in 2002 (including leucoxene) and rutile were
approximately 5.64 million tons and approximately
0.35 million tons, respectively ( http://www.indexmundi.
com/en/commodities/minerals/titanium/titanium_t15.
html ). The recovery of titanium from secondary sources
probably does not exceed 1% of the total production.
Two main production processes are used for prepar-
ing commercial titanium dioxide pigments: sulfate and
chloride processes.

2 METHODS AND PROBLEMS
OF ANALYSIS

Methods applied to the detection of titanium in
water and food include spectrography and photom-
etry. Although various atomic absorption techniques
have also been reported, the use of a high-tempera-
ture reducing fl ame is desirable, because of its poor
atomization and its tendency to form refractory oxides.
Inductively coupled plasma optical emission spec-
trometry (ICPOES) techniques have been developed
for the rapid determination of titanium in foods after
acid digestion (Lomer et al ., 2000). TiO 2 is usually meas-
ured as the metal. Inductively coupled argon plasma
atomic emission spectroscopy (ICP-AES) is an alterna-
tive method for determining titanium dioxide in air,
with detection limits in the parts per billion range and
excellent recovery (96%; NIOSH, 1994d). This method
can also be used to assay titanium in urine and tissues,
with a detection level of 20 ppb and a good level of
recovery (86%; NIOSH, 1994a).
Proton-induced X-ray emission spectroscopy has
also been used with practical detection limits of approx-
imately 0.001

3.2 Uses
Titanium metal fi nds an extensive number of appli-
cations in the aircraft and spacecraft industries because
of its very high tensile strength, light weight, extraor-
dinary corrosion resistance, and its ability to withstand
extreme temperatures. When used for these purposes,
titanium is usually used in the form of alloys, which
are stronger and more resistant against corrosion than
is the metal itself. Because of its resistance to corrosion
and its chemical inertness, titanium is used widely in
the chemical industry; for example, as tubing and for
the lining of vessels used in the production of nitric
acid and acetaldehyde. Its resistance to corrosion
means that titanium is also useful in the paper pulp
industry. Titanium is the newest metallic biomaterial
among the most popular metallic alloys (Niinomi,
2002). Titanium and its alloys continue to receive much
attention in medical and dental fi elds because of the
balance between their excellent mechanical proper-
ties and corrosion resistance; they are used mainly

g of
titanium per drop of water (Johansson et al ., 1975).
X-ray fl uorescence has been used widely for the
determination of titanium in air, water, and biologi-
cal samples; the detection limit for titanium in air is

µ g for titanium in air and <0.001 µ