Chemistry Reference
In-Depth Information
for implant devices that replace failed hard tissue, for
example, artifi cial hip or knee joints, bone plate, and
dental implants. Titanium and its alloys are also used
in dental products, such as crowns, bridges, and den-
tures.
Titanium dioxide (TiO
2
) is the most common
titanium compound; it constitutes almost 95% of all
titanium consumed. Titanium dioxide is the most com-
mon white synthetic pigment used in the paint indus-
try. It has many favorable properties: ready availability,
a comparatively cheap price, extreme whiteness and
brightness, and a high index of refraction. On the basis
of these characteristics, titanium dioxide is used exten-
sively as a white pigment in paints, lacquers, enamels,
paper coatings, and plastics. Because of its effective-
ness as a sunscreen toward short-wave ultraviolet
radiation, titanium oxide is included within a variety
of drugs and cosmetics. It is also used as a color addi-
tive in confections, dairy products, and bread fl ours as
a replacement fl our-bleaching agent. Titanium diox-
ide serves as a clouding agent incorporated into dry
beverage mixes and is used in tobacco wrappings and
tobacco substitutes. Titanium dioxide is also used in the
pharmaceutical industry as a constituent of tablets.
Titanium tetrachloride (TiCl
4
) is another commer-
cially important titanium derivative that is used as an
intermediate in the production of titanium metal and
titanium pigments and as a component and catalyst in
the chemical industry. Titanium chloride (TiCl
3
), which
is prepared by the reduction of titanium tetrachloride,
serves as a coloring agent and as a catalyst in various
chemical processes.
Typical diets may contain approximately 0.3-0.5 mg
titanium (Poole and Johnston, 1969; Schroeder
et al
.,
1963; Tipton and Stewart, 1969).
4.1.2 Water, Soil, and Ambient Air
It has been reported that titanium concentrations
range from 2-107
g/L in freshwater in Canada and
the United States (Durum and Haffty, 1961) and 0.5-
15
µ
g/L) in drinking
water in the United States (Durfor, 1963). Titanium
concentrations in seawater are mostly approximately
0.6-1
µ
g/L (mostly approximately 2
µ
g/L have been reported
(Bowen, 1966; Ishibashi, 1968; Silvey, 1967).
The titanium content of soil generally ranges from
0.3-6%, with high levels found in the vicinity of power
plants because of the combustion of coal (Klein and
Russell, 1973).
Titanium concentrations in the atmosphere are
comparatively low. Annual average concentrations in
urban air are mostly <0.1
µ
g/L, but values up to 9
µ
g/m
3
, and they are lower
still in rural air (EPA, 1973). Air concentrations up to
0.5
µ
g/m
3
have been reported in urban and industrial-
ized areas (EPA, 1973; Giauque
et al
., 1974; Japan Envi-
ronmental Sanitation Centre, 1971). The daily intake
from urban air is approximately 1-5
µ
µ
g; it is likely to
be <1
g in rural areas (Schroeder
et al
., 1963; Wool-
rich, 1973). Compared with the amount of titanium
absorbed from food, the intake of titanium from the air
is negligible: under most conditions, <1% to the total
daily intake.
µ
4.2 Working Environment
Occupational exposure to titanium occurs princi-
pally in the form of dust; inhalation is the common
route of exposure. High exposure levels have been
reported from mining, from the production of the
metal, and from the production and processing of
titanium dioxide, carbide, and hydride. Typical dusty
operations include the crushing, grinding, mixing,
and sieving of rutile concentrates. High exposure to
titanium compounds in the air has also been reported
from the manual handling, screening, and packaging
of titanium hydride powder (Skurko and Brahnova,
1973). Exposure to fumes and vapors occurs in the han-
dling of titanium tetrachloride. Exposure to titanium
tetrachloride may also occur in the reduction proc-
ess, where workers are exposed to titanium tetrachlo-
ride and titanium oxychloride vapors and to titanium
dioxide particulates (Garabrant
et al
., 1987). Exposure
may occur at any stage during the mining of ores and
the preparation of titanium dioxide and in any of the
industries in which the powder is stored and used.
The American Conference of Governmental Industrial
4 ENVIRONMENTAL LEVELS
AND EXPOSURES
4.1 General Environment
4.1.1 Food and Daily Intake
Titanium is poorly absorbed by plants and animals
and is retained to only a certain extent. High levels of
titanium in food products can be detected, however,
when soil is contaminated by fl y-ash fallout or tita-
nium-containing sewage residues (used as fertilizers)
and when titanium dioxide is used as a food whitener.
High concentrations of titanium in certain types of
cheese result from the addition of titanium dioxide as
a whitener and as an aging accelerator. Food, which is
considered to be the most important source of expo-
sure to titanium, contributes >99% of the daily intake
of the element. There is no relevant tolerable intake for
titanium against which to compare estimated dietary
intake (Joint Food Safety and Standards Group, 2000).
