TITANIUM DIOXIDE 1. Exposure Data - IARC Monographs

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titanium, dioxide, rutile, that, particles, White, Titanium, with, anatase, rutile,, oxide;, primary, brookite, most, (Banfield, dioxide(B), brookite,, commercial, Chemical, aggregates, Head, Veblen,, from, Horse, impurities, structure, products, g/cm3;, Anatase,, have

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TITANIUM DIOXIDE
Titanium dioxide was considered by a previous Working Group in October 1988
(IARC, 1989). Since that time, new data have become available, and these have been
included in the present monograph and taken into consideration in the evaluation.
1. Exposure Data
1.1 Chemical and physical data
1.1.1 Nomenclature
Chem. Abstr. Services Reg. No.: 13463–67–7, titanium dioxide; 1317–70–0, anatase
titanium dioxide; 1317–80–2, rutile titanium dioxide
Chem. Abstr. Name: Titanium dioxide
IUPAC Systematic Name: Titanium dioxide
Synonyms: CI: 77891; dioxotitanium oxide; E 171; NCI-CO4240; Pigment White 6;
titania; titanic oxide; titanium oxide; titanium (IV) oxide; titanium peroxide
1.1.2 Molecular formula and relative molecular mass
TiO2 Relative molecular mass: 79.90
1.1.3 Chemical and physical properties of the pure substance
Description: Fine white powder (Windholz, 1983)
Crystal structure
Four naturally occurring titanium dioxide polymorphs exist: rutile, anatase, brookite
and titanium dioxide(B) (Banfield & Veblen, 1992). Anatase and rutile are tetragonal,
brookite is orthorhombic and titanium dioxide(B) is monoclinic. In all four
polymorphs, titanium is coordinated octahedrally by oxygen, but the position of the
octahedra differs between polymorphs. The structure of rutile is the most dense and
its unit cell is the smallest. Anatase has four formula units per unit cell with
a = 0.379 nm and c = 0.951 nm; rutile has two with a = 0.459 nm and c = 0.296 nm;
brookite has eight with a = 0.917 nm, b = 0.546 nm and c = 0.514 nm; and titanium
194 IARC MONOGRAPHS VOLUME 93
dioxide(B) has eight with a = 1.216 nm, b = 0.374 nm, c = 0.651 nm and β = 107.29°
(Banfield & Veblen, 1992). Only the structures of rutile (titanium dioxide-rutile) and
anatase (titanium dioxide-anatase) are reported in commercial products.
Density of ideal minerals: Anatase, 3.79 g/cm3; rutile, 4.13 g/cm3; brookite,
3.99 g/cm3; and titanium dioxide(B), 3.64 g/cm3 (Banfield & Veblen, 1992)
Refractive index: Anatase, 2.561, 2.488; rutile, 2.605–2.616, 2.890–2.903; and
brookite, 2.583, 2.700 (Phillips & Griffen, 1981)
Hardness on Moh’s scale: Anatase, 5.5–6; rutile, 6–6.5; and brookite, 5.5–6 (Harben
& Kuzvart, 1996)
Solubility: Soluble in sulfuric acid and alkalis; insoluble in water (Weast, 1985)
Spectroscopy: X-Ray diffraction patterns for anatase and rutile are available from the
International Center for Diffraction Data (2005), which maintains the powder
diffraction file.
Chemical composition: Natural rutile, anatase and brookite contain impurities of up to
≈2% that include iron, chromium, vanadium, aluminium, niobium, tantal, hafnium
and zirconium (Heaney & Banfield, 1993) and account for slight variations in density,
colour and indices of refraction. Since most commercial titanium dioxide is
manufactured from natural material by dissolution of the parent mineral and
reprecipitation as fine particles with the structure of anatase or rutile (referred to as
titanium dioxide-anatase or titanium dioxide-rutile), most but not all of these chemical
impurities are generally removed.
Other characteristics: Titanium dioxide is an ultraviolet (UV)-activated catalyst, and
organic polymers that are in contact with it degrade under UV radiation. Anatase is
10 times more active than rutile and responds to slightly different wavelengths
(Braun, 1997).
1.1.4 Technical products and impurities
Trade names for titanium dioxide include Aeroxide, A-Fil Cream, Atlas white
titanium dioxide, Austiox, Bayertitan, Calcotone White T, Comet, Cosmetic White C47–
5175, Cosmetic White C47–9623, C-Weiss 7, Flamenco, Hitox, Hombitan, Hombitec,
Horse Head A-410, Horse Head A-420, Horse Head R-710, Kemira, KH 360, Kronos
titanium dioxide, Levnox White RKB, Pretiox, Rayox, Runa RH20, Rutile, Rutil RC,
Rutiox, Tichlor, Tiofine, TiO2 Hombitan, Tiona T.D., Tioxide, Tipaque, Ti-Pure, TiSelect, Titafrance, Titan, Titania, Titandioxid, Titanium White, Titanox, Titanox 2010,
Trioxide(s), Tronox, Tytanpolr, Unitane products (various), UV-Titan, 1700 White and
Zopaque.
(a) Particle size
Titanium dioxide particles are referred to as primary, aggregates or agglomerates.
Primary particles are single crystals that are bound by crystal planes. Aggregates are
TITANIUM DIOXIDE 195
sintered primary particles that are connected by crystal faces. Agglomerates are multiple
primary particles and aggregates that are held together by van der Waal’s forces.
Scattering of light by titanium dioxide is maximized in particles that are 0.2–0.3 μm
in diameter, and most commercial products that are used as pigments have modal primary
particle sizes within this range. The range of ultrasonically dispersed primary particles
and aggregates is narrow, and generally ranges from <0.1 to 0.5 μm (Braun, 1997; Linak
et al., 2002; Swiler, 2005). A recent study showed that commercial pigments contain
almost no particles <0.1 μm. This range may not apply to bulk material, which contains
aggregates that are not broken down during industrial use (Braun, 1997).
Non-pigmentary titanium dioxide is composed of either uncoated manufactured
titanium dioxide (both titanium dioxide-anatase and titanium dioxide-rutile) or ground
natural rutile. In general, these products contain coarser particles than pigmentary
titanium dioxide (Linak et al., 2002).
Ultrafine titanium dioxide particles (nanoparticles) range in size from 1 to 150 nm
(Linak et al., 2002), with a modal primary particle size of 10–50 nm. They are generated
by sol-gel synthesis and the wide variation in their morphology and size is controlled by
the pH of the gel.
Primary particles generally form aggregates and agglomerates and are not normally
found as discrete particles. In commercial products, the particle size of pigmentary and
ultrafine material is approximately equal because of aggregation and agglomeration
(American Chemistry Council, 2005).
Titanium dioxide has also been produced as engineered nanomaterials, which may be
equidimensional crystals or sheets and are composed of either titanium dioxide-rutile or
titanium dioxide-anatase. A tubular structure has been produced from scrolling layers of
titanium dioxide-anatase, which results in fibres with an outer diameter of about 6 nm and
an inner tube of about 3 nm (Barnard et al., 2005). Non-scrolled nanofibres have also
been produced from titanium dioxide-anatase and titanium dioxide(B) with diameters of
20–100 nm and lengths of 10–100 μm (Pavasupree et al., 2005).
(b) Types of titanium-dioxide pigment
According to the American Society for Testing and Materials (ASTM, 1988) D476–
84 standard, four types of titanium dioxide pigment exist (Schurr, 1981; Fisher &
Egerton, 2001):
Type I (94% titanium dioxide min.) is a titanium dioxide-anatase pigment that chalks
[forms a layer of loose pigment powder on the surface of weathered paint film] freely and
is used in white interior and exterior house paints.
Type II (92% titanium dioxide min.) is a titanium dioxide-rutile pigment that has a
medium resistance to chalking and is used in varying amounts in all types of interior
paints, enamels and lacquers.
Type III (80% titanium dioxide min.) is also a titanium dioxide-rutile pigment that has
a medium resistance to chalking and is used principally in alkyd and emulsion flat-wall
paints.
196 IARC MONOGRAPHS VOLUME 93
Type IV (80% titanium dioxide min.) is another titanium dioxide-rutile pigment that
has a high resistance to chalking; it is used in exterior paints and has excellent durability
and gloss retention.
The Japanese grading system, the JIS K5116–1973, specifies four grades of titanium
dioxide-rutile, three of which contain at least 92% titanium dioxide and the fourth
contains a minimum of 82%. The type of coating in each grade is also specified (Fisher &
Egerton, 2001).
(c) Extenders, impurities and coatings
Titanium dioxide extenders were used in commercial pigments in the past, but are not
generally employed now. Calcium sulfate (Braun, 1997) and barium sulfate (Fisher &
Egerton, 2001) were commonly used during the early years of production, and other
materials that may have been used as extenders for white pigment include calcium
carbonate, alumina, silica and kaolin (Linak et al., 2002).
Titanium dioxide-anatase pigments may contain titanium dioxide-rutile. Before
coating, titanium dioxide-anatase produced by the sulfate process contains both
phosphorous and sulfate that are concentrated at the particle surface. In addition, uncoated
titanium dioxide-anatase pigments retain about 0.3% niobium pentoxide and
0.3% phosphorus pentoxide from the ore and up to 0.2% alumina that is added during
manufacture (Braun, 1997).
Prior to coating, titanium dioxide-rutile pigments that are produced by chlorination
contain about 1% alumina, which is concentrated at the surface of the particles (Braun
1997), but not titanium dioxide-anatase.
With the exception of non-pigmentary titanium dioxide such as ground rutile and
titanium dioxide-anatase that are used as food additives, all commercially produced
titanium dioxide is coated by a variety of oxides and oxyhydrates by aqueous
precipitation techniques. These coatings improve dispersibility, dispersion stability,
opacity, durability and gloss. They form a barrier between the titanium dioxide and
organic substances, such as those found in paints, and prevent contact catalysis. In some
cases, organic or silicone treatments may be added after initial coating. Titanium dioxiderutile pigments generally contain 1–15% of coatings and titanium dioxide-anatase
pigments contain 1–5% of coatings. The most common coatings are composed of
oxyhydrates and oxides of aluminium and silicone. Oxides and oxyhydrates of zirconium,
tin, zinc, phosphorous, cerium and boron are also used (Linak et al., 2002). Table 1.1
(American Chemistry Council, 2005) gives the types of coating that are used in
decreasing order of importance.
The thickness of these coatings is variable but may be only a few atom layers. They
are generally coherent over the surface of the titanium dioxide particle (American
Chemistry Council, 2005), but some titanium oxide and titanium hydroxide may also be
present on the surfaces (Braun, 1997). The thinness of the coatings precludes most
techniques of structural analysis and their atomic structure therefore remains largely
unknown (Braun, 1997). The composition (but not necessarily the atomic structure) of the
TITANIUM DIOXIDE 197
alumina coatings are γ-AlOOH (bohemite), α-AlOOH (diaspor) and γ-Al(OH)3
(hydrargillite). The silica coatings may be fluffy, and consist of polymerized silicic acid or
a dense, true shell of glass. Ultrafine titanium dioxide is also coated; examples of coatings
are given in Table 1.2.
Coating with alumina and silica can more than double the surface area (Braun, 1997).
The surface area of untreated pigment ranges from 8 to 10 m2/g, while treated pigment
surface areas generally span 8–19 m2/g and matt-finish pigments (that have high levels of
alumina) can extend up to 35 m2/g. Surface areas of the ultrafine products are in the range
of 35–100 m2/g (American Chemistry Council, 2005).
Titanium dioxide-coated surface and pigments are hydrophilic; those coated with
silicones are not used as pigment because they are hydrophobic.
Table 1.1. Types of coating used for common grades of titanium dioxide pigment
(normally titanium dioxide-rutile)
Surface treatment type Composition, range (wt %) Application
Alumina/TMP Al2O3, 1.0–5.5
Total carbon, <0.3
Paint/coatings
Alumina/zirconia/TMP Al2O3, 1.0–5.0
ZrO2, 0.3–1.0
Total carbon, <0.3
Paint/coatings
Alumina/silica/siloxane Al2O3, 1–6
SiO2, 0.3–3
Total carbon, <0.3
Plastics
Alumina/silica/TMP Al2O3, 1.0–6.0
SiO2, 0.5–13.0
Total carbon, <0.3
Paint/coatings/plastics
Alumina/TME Al2O3, 1.0–3.5
Total carbon, <0.3
Paint/coatings
Alumina/zirconia/TME Al2O3, 1.0–5.0
ZrO2, 0.3–1.0
Total carbon, <0.3
Paint/coatings
Alumina/silica/TME Al2O3, 1.5–5.0
SiO2, 1.5–3.5
Total carbon, <0.3
Paint/coatings
Alumina/silica/silane Al2O3, 1.0–6.0
SiO2, 0.3–3
Total carbon, <0.3
Plastics
From American Chemistry Council (2005)
TME, trimethylol ethane; TMP, trimethylol propane; wt, weight
198 IARC MONOGRAPHS VOLUME 93
Table 1.2. Relative proportiona of the production of common grades of ultrafine
titanium dioxide used in sunscreens with different types of coating
Organic Inorganic
None Silica
5–25%
Alumina 1–25% Silica 1–10% +
alumina 5–15%
Sodium metaphosphate
1–5%
None 2 4 3 4 1
Stearate 5–15% as carbon 16
Butyl glycol dicaprylate 60% +
stearate 5%
1
Methicone max. 11% 1 1
Dimethicone 1–10% 2 4
Dimethicone/siloxane 2% as
SiO2
2
Dimethicone/methicone
copolymer 1–10%
2 2 4
Simethicone 5% (as SiO2) +
water 13%
2
Trimethylsiloxysilicone 1–10% 4
Polyvinyl-pyrrolidone max. 3% 1
Alkyl silane 2.7–3.7% as carbon 1
Glycerin max. 1% 1
Alginate 1–5% 1
From American Chemistry Council (2005)
a 16=high, 1=low
1.1.5 Analysis
Exposure to particulates in occupational environments is generally determined
gravimetrically. The behaviour of titanium dioxide in air and its deposition in the
respiratory tract upon inhalation are important factors in human exposure, and are
determined by the aerodynamic diameter of the particles. The aerodynamic diameter can
be measured by impactors and is dependent upon the geometric diameter, [material]
density and shape [factor] of the aggregates. Most commonly, the size distribution of
airborne particles is expressed as the mass median aerodynamic diameter (MMAD) and
the geometric standard deviation. Several dust fractions are often identified, namely,
‘total’ dust, inhalable dust and respirable dust.
TITANIUM DIOXIDE 199
Inhalable dust approximates the fraction of airborne material that enters the nose and
mouth during breathing and is therefore available for deposition anywhere in the
respiratory tract (International Standards Organization, 1995; Health and Safety
Executive, 2000). The inhalable fraction depends on the prevailing movement of air
around the exposed person and whether breathing is by the nose or mouth. It is, however,
possible to define target specifications for sampling instruments that approximate the
inhalable fraction and these are provided by the International Standards Organization
(1995). In the United Kingdom, the standard sampling devices for measuring inhalable
dust are the multiorifice sampler and the Institute of Medicine (IOM) sampler (Health and
Safety Executive, 2000).
Respirable dust approximates the fraction of airborne material that penetrates the gasexchange region of the lung. The respirable fraction varies between individuals; however,
it is possible to define a target specification for sampling instruments that approximates
the respirable fraction for an average person (International Standards Organization, 1995).
Respirable dust is generally collected using a cyclone preselector (Health and Safety
Executive, 2000).
The term ‘total’ dust refers to total particulates that are represented (in North America
at least) by the material that is collected by a closed-face three-piece plastic sampling
cassette that holds a 37-mm filter (Eller & Cassinelli, 1994). The term ‘total’ dust is not
equivalent to all airborne dust; in fact, measurements of inhalable dust by the IOM
sampling head are 1.0–2.5 times higher than ‘total’ dust levels using a closed-face 37-mm
filter cassette, depending on the aerodynamic diameter of the particles (Werner et al.,
1996).
Analysis of different types of coatings is accomplished by transmission electron
microscopy equipped with energy-dispersive X-ray spectroscopy.
1.2 Production and use
1.2.1 Production
The manufacture of pure titanium white for use as a pigment (anatase form) was first
reported in 1923 in France. The growth of the production and use of titanium white
pigments began in the early 1930s and continued until recently, but the rate has now
decreased. In 2004, worldwide production was estimated at 4.4 million tonnes (Swiler,
2005).
(a) Sources
Titanium dioxide pigments are manufactured from a variety of ores that contain
ilmenite (FeTiO3), rutile, anatase and leucoxene (TiO2.xFeO.yH2O), which are mined
from deposits located throughout the world. Titanium may also be recovered from slag
produced during iron smelting and from synthetic rutile produced from ilmenite.
200 IARC MONOGRAPHS VOLUME 93
Large deposits of titanium dioxide occur in association with igneous rocks and as
heavy mineral deposits in unconsolidated sands (Garnar & Stanaway, 1994; Chang,
2002). Major igneous deposits are found in Brazil, Canada, Norway, the Russian
Federation and the Ukraine (Chang, 2002).
Important heavy mineral sands are found along the eastern and western coasts of
Australia, the eastern coast of South Africa, the southeastern coast of the USA, the west
coast of South Island, New Zealand, the eastern coast of China, the northeastern coast of
Sri Lanka, at various locations along the southern coast of India, in coastal Malaysia and
in alluvial deposits in Sierra Leone and China (Chang, 2002).
Anatase, brookite and titanium dioxide(B) are common minor constituents in soils
and sediments, particularly those derived from titanium-rich rocks. Rutile is a common
accessory mineral in a wide variety of crustal and mantle-derived rocks and in sediment
and sedimentary rocks (Heaney & Banfield, 1993).
Ilmenite is found in beach sand in existing or fossil coastlines and is an important raw
material in titanium dioxide production. Surface processes alter the ilmenite in these
deposits to produce submicroscopic mixtures of minerals that include anatase, rutile and
amorphous phases. Mixtures that contain as much as 90% titanium dioxide are referred to
as leucoxene. Leucoxene is recovered from some deposits and treated separately.
However, the quantities produced are small in comparison with those of ilmenite. The
concentrates obtained from ilmenite sand, which are depleted of iron, are generally richer
in titanium dioxide than those from the massive deposits. Other elements in these
concentrates include magnesium, manganese and vanadium that are present in the
ilmenite, and aluminum, calcium, chromium and silicon (Kischkewitz et al., 2002).
The second most commonly available ore is the buff-coloured mineral rutile, which
contains about 95% titanium dioxide with smaller amounts of iron and other impurities.
The rutile contained in primary rocks cannot be extracted. Only sands in which rutile is
accompanied by zircon and/or ilmenite and other heavy minerals can be used as raw
materials. Rutile sands are mostly found in Australia, Sierra Leone and South Africa. The
importance of mineral rutile to the titanium dioxide industry is waning. In the 1970s, it
accounted for 20% of the feedstock, but now accounts for less than 10% due to
diminishing reserves (Kischkewitz et al., 2002; Linak & Inoguchi, 2005).
Anatase, like rutile, is a modification of titanium dioxide. The largest reserves of this
mineral are found in carboniferous intrusions in Brazil. Techniques for preparation of the
ore produce concentrates that contain 80% titanium dioxide, and further concentration to
90% titanium dioxide is possible by treatment with hydrochloric acid (Kischkewitz et al.,
2002).
(b) Processing
There are five stages in the manufacture of pigmentary titanium dioxide. First,
titanium dioxide ore is converted to either aqueous titanyl sulfate solution or anhydrous
titanium tetrachloride. These intermediates are then converted to crystalline, size-specific
pigmentary particles of titanium dioxide-rutile or titanium dioxide-anatase. The pigment
TITANIUM DIOXIDE 201
is coated, in some cases involving a grinding step, and then filtered, washed and dried.
Finally, the pigment agglomerates may be ground to reduce their size without breaking
the primary titanium dioxide particles (Braun, 1997).
Most ores are concentrated or otherwise processed to increase the titanium dioxide
content before they are suitable as a raw material for pigment production. Impurities such
as iron and alkaline earth elements colour the ores from buff to black and must be
removed to obtain a clean white titanium dioxide pigment (Kischkewitz et al., 2002;
Linak & Inoguchi, 2005).
Direct use of ilmenites has decreased due to their high iron content. A digestion
process is employed to produce iron sulfate heptahydrate from ilmenite. When iron
sulfate is not required as a product, metallurgical recovery of iron from iron-rich ilmenites
and production of a titanium-rich slag are increasingly being used (Kischkewitz et al.,
2002; Linak & Inoguchi, 2005).
Titanium dioxide pigment is produced from titanium mineral concentrates by either
the chloride process or the sulfate process. In the sulfate process, ilmenite or titanium slag
is reacted with sulfuric acid. Titanium hydroxide is then precipitated by hydrolysis,
filtered and calcined. In the chloride process, rutile is converted to titanium tetrachloride
by chlorination in the presence of petroleum coke. The titanium tetrachloride is oxidized
by air or oxygen at about 1000°C, and the resulting titanium dioxide is calcined to remove
residual chlorine and any hydrochloric acid that may have formed in the reaction.
Aluminium chloride is added to the titanium tetrachloride to ensure that virtually all the
titanium is oxidized into the rutile crystal structure. Although either process may be used
to produce pigment, the decision to use one process instead of the other is based on
numerous factors, including the availability of raw materials, freight and waste disposal
costs. In finishing operations, the crude form of the pigment is milled to produce a
controlled distribution of particle size and the surface is treated or coated to improve its
functional behaviour in different media. Typical surface treatments include alumina,
organic compounds (e.g. polyols, esters, siloxanes, silanes) and silica (Kischkewitz et al.,
2002; Gambogi, 2003).
Each producer of titanium dioxide has its own purity requirements and hence places
different values on certain physical properties. For example, Japanese producers tend to
prefer ilmenite which has a higher ferrous oxide content but a lower titanium dioxide
content than the ores generally favoured by European producers (Kischkewitz et al.,
2002; Linak & Inoguchi, 2005).
(c) Capacity, production and consumption
In 2004, world production of titanium mineral concentrates had increased to
5.2 million tonnes from 4.6 million tonnes in 2000. Approximately 95% is used as
feedstock for titanium dioxide and the remainder is used in titanium metal alloys. In 2004,
the leading supplier of titanium feedstock was South Africa (25%), followed by Australia
(21%), Canada (14%), China (8%), the Ukraine (7%) and Norway (7%) (Linak &
Inoguchi, 2005).
202 IARC MONOGRAPHS VOLUME 93
Approximately 60 plant sites worldwide (outside of China) produce titanium dioxide,
with an average annual capacity of 60 000 tonnes. Table 1.3 presents world titanium
dioxide capacity by region and process for 1993, 1998, 2002 and 2005 (Linak &
Inoguchi, 2005).
In recent years, most increases in capacity have been through the development of
small plants in China and other less developed regions. Until recently, global capacity had
been growing faster than demand, resulting in oversupply and erosion of prices. In real
terms, prices have been decreasing on average by about 1% per year for the past 20 years
(Linak & Inoguchi, 2005).
For environmental, economic and qualitative reasons, chloride process plants
continue to be favoured over sulfate plants in industrialized countries, particularly for new
production facilities. Operators of sulfate process plants have had to invest in waste acid
recycling facilities to extend operating lives. In addition, the production of rutile pigment
from the chloride process has increased (Linak & Inoguchi, 2005).
Titanium dioxide is used in more than 170 countries. The major exporting regions are
North America and Australia, and most of the countries in the rest of the world are net
importers. Table 1.4 presents world supply and demand for titanium dioxide in 1997,
2001 and 2004 (Linak & Inoguchi, 2005).
1.2.2 Use
Titanium dioxide is valued for its opacifying strength (commonly called hiding
power) and brightness. Other important features of titanium dioxide pigments are
excellent resistance to chemical attack, good thermal stability and resistance to UV
degradation. Rutile pigment is more resistant to UV light than anatase, and is preferred for
paints, plastics, especially those exposed to outdoor conditions, and inks. Anatase pigment
has a bluer tone than the rutile type, is less abrasive and is used mainly in indoor paints
and in paper, ceramics, rubber and fibres manufacture. Both rutile and anatase pigments
can be made more resistant to photodegradation by coating the pigment particles, which
also improves their dispersibility, dispersion stability, opacity and gloss. Usually alumina,
silica, zirconia or a combination of these is used; silica is most effective in retarding the
photoactivity of the pigment, while alumina is most effective in enhancing dispersibility
and binder compatability. Generally, rutile pigments contain 1–15% coating and anatase
pigments contain 1–5%. The higher levels of coating are given to pigments that are
typically used for applications such as flat (low-gloss) paints (Linak & Inoguchi, 2005).
The major consumer industries for titanium dioxide pigments are mature sectors in
high-resource countries where they are used for surface coatings, paper and paperboard
and plastics. Therefore, consumption of titanium dioxide tends to parallel general
economic trends. Paint and coating applications have the largest global use, and plastics
and paper account for most of the remainder. World consumption of titanium dioxide by
end-use in 2001 was: coatings, 55%; plastics and rubber, 24%; paper, 12%; printing inks,
3%; and other, 6%; that in 2005 was: coatings, 58%; plastics and rubber, 23%; paper, 11%;
TITA
N
IU
M
D
IO
X
ID
E
203
Table 1.3. World capacity for titanium dioxide (thousand tonnes, gross weight)
Region 1993 1998 2002 2005
S C Total S C Total S C Total S C Total
North America 202 1288 1488 178 1436 1614 134 1656 1790 80 1717 1797
Central and
South America
55 0 55 60 0 60 60 0 60 96 0 96
Western Europe 875 317 1192 913 405 1318 925 472 1397 862 547 1409
Central and
eastern Europe
195 0 195 203 0 203 217 0 217 234 0 234
Africa and Middle
East
35 50 85 40 80 119 40 100 140 25 100 125
Japan 270 50 319 272 52 324 259 68 327 240 68 308
China – – – – – – 258 408 666 658 15 673
Oceania and other
Asia
224 114 338 291 184 475 – – – 141 404 545
Total 1856 1819 3672 1957 2157 4113 1893 2704 4597 2336 2857 5187
From Linak & Inoguchi (2005)
C, chloride process; S, sulfate process
204 IARC MONOGRAPHS VOLUME 93
Table 1.4. World production and consumption of titanium dioxide (thousand
tonnes, gross weight)
Region 1997 2001 2004
P C P C P C
North America
Canada
Mexico
USA
75
102
1340
105
37
1129
68
124
1340
90
65
1100
76
124
1511
104
64
1162
Central and South America
Brazil
Other
79
0
108
60
78
0
111
60
80
0
124
85
Western Europe 1113 1099 1150 1100 1254 1183
Central and eastern Europe 136 125 155 155 155 155
Africa and Middle East
Saudi Arabia
Other Middle East
South Africa
Other Africa
50
0
30
0
10
60
25
15
55
0
30
0
10
65
20
35
90
0
20
0
30
120
28
45
Japan 241 269 257 246 253 238
Oceania and other Asia
Australia
China
India and Pakistan
Indonesia
Malaysia
Philippines
Republic of Korea
Singapore
Southeast Asia
Taiwan (China)
Thailand
Other
160
102
50



35

77
68


40
170
70



100

145
71


181
147
44

50

42
41

123

0
66
256
77

28

118
16

66

108
200
350
52
0
50
0
40
45

120
0
0
40
540
82
49
15
33
120
30

66
71
29
Total 3658 3638 3885 3792 4420 4423
C, consumption; P, production
From Linak & Inoguchi (2005)
TITANIUM DIOXIDE 205
and other, 8% (Linak & Inoguchi, 2005). Some other uses of titanium dioxide are in
catalysts, ceramics, coated fabrics and textiles, floor coverings and roofing granules
(Gambogi, 2005; Swiler, 2005).
Despite their lower price, anatase-grade pigments account for only 10% of total
global production. About two-thirds of the total anatase supply is used in markets where
quality is less important, such as paper, low-priced emulsion paints, or tiles and enamels.
Only one-third of the anatase is used in applications for which its specific properties are
highly valued, such as when a bluish tint is desired in some plastics. Anatase is also used
because of its photocatalytic properties; total global demand for its use as an active
material for the removal of nitrogen oxide compounds from waste gases of coal-fired
power plants and for the cleaning of exhaust gases of diesel engines is 15 000 tonnes per
year (Linak & Inoguchi, 2005; Swiler, 2005).
Traditionally, the industry has produced a wide variety of grades of titanium dioxide
that are tailored for specific applications. In recent years, producers have introduced socalled ‘multipurpose products’ to try to reduce the number of grades needed in an effort to
increase operating efficiency. For example, in the paint market, titanium dioxide
manufacturers propose a universal product that is acceptable for use in flat (low-gloss)
and enamel (high-gloss) coatings (Linak & Inoguchi, 2005).
Some products with coarse particle sizes are obtained at an intermediate step (before
coating with inorganic oxides) in the manufacture of pigmentary titanium dioxide.
Manufacturers propose a ‘buff’ titanium dioxide that is made by grinding rutile ore to
yield a product with a 95% titanium dioxide content that can be used as a partial
replacement for white titanium dioxide in formulations that are tinted with other colour
pigments. Total estimated global production of pigment by this process is about
10 000 tonnes per year (Kischkewitz et al., 2002; Linak & Inoguchi, 2005).
Ultrafine grades of titanium dioxide (particle size, 1–150 nm), which transmit visible
light but scatter UV radiation, are used as UV blockers in sunscreens and plastics,
catalysts and colour pigment precursors and in electroceramics (Kischkewitz et al., 2002;
Linak & Inoguchi, 2005).
Relatively small quantities of titanium dioxide are used for non-pigmentary purposes.
The estimated global market is 110 000 tonnes per year, and the largest user sectors are
enamels and ceramics (25–30%), glass and glass ceramics (25–30%), electroceramics
(10–15%), catalysts and catalyst supports (10–15%) and welding fluxes (10–15%)
(Kischkewitz et al., 2002; Linak & Inoguchi, 2005).
1.3 Occurrence and exposure
1.3.1 Natural occurrence
Titanium is the ninth most abundant element in the world, it is five times less
abundant than iron but 100 times more abundant than copper. The chemical composition
206 IARC MONOGRAPHS VOLUME 93
of titanium dioxide is described in detail in Section 1.1.3 and its sources in Section
1.2.1(a).
1.3.2 Occupational exposure
On the basis of a National Occupational Exposure Survey, conducted in the USA
between 1981 and 1983, the National Institute for Occupational Safety and Health
(NIOSH, 1983) estimated that 2.7 million workers (2.2 million men and 0.5 million
women) were potentially exposed to titanium dioxide. [This estimate is based on a survey
of companies and did not involve measurements of actual exposure; for many workers,
very low levels and/or incidental exposures to titanium dioxide may be incurred.]
No estimate of the number of workers currently exposed to titanium dioxide was
available to the Working Group.
(a) Manufacture of titanium dioxide
The highest levels of exposure within a titanium dioxide manufacturing plant are
generally observed in the milling and packing areas (Fryzek et al., 2003). In these areas,
titanium dioxide is finely processed by micronizers, and dust from the bags used for
shipment may be dispersed through the air during bagging by the packers. Lower, but
consistent, exposure to titanium dioxide may be incurred by treatment operators, who are
involved in the addition of special coatings to and treatments of titanium dioxide before
the product is finally milled and packed. Although maintenance mechanics are not
exposed to titanium dioxide on a daily basis, they may experience short periods of heavy
exposure during routine maintenance and repair activities associated with precipitation of
titanium dioxide and subsequent processes or post-oxidation steps. Minimal exposure to
titanium dioxide is incurred by workers who are involved in the initial processing and
refinement of the product. In addition, general labourers or helpers, laboratory workers
who work mainly in the laboratories to monitor the product and workers who handle raw
ore also have minimal exposure to titanium dioxide.
Fryzek et al. (2003) reported results from 914 personal full-shift or near full-shift air
samples for ‘total’ titanium dioxide that were obtained from four plants between 1976 and
2000 (Table 1.5). Eighteen of these samples appeared to the authors to be unrealistically
high and were limited to 50 mg/m3. The highest exposures were observed for packers,
micronizers and workers involved in shovelling spilled titanium dioxide into bags (n=686;
mean, 6.0 mg/m3). Exposure levels decreased over time from a mean of 13.7 mg/m3
(n=21) in 1976–80 to 7.9 mg/m3 (n=87) in 1981–85, 6.4 mg/m3 (n=210) in 1986–90,
5.3 mg/m3 (n=239) in 1991–95 and 3.1 mg/m3 (n=357) in 1996–2000.
In seven titanium dioxide manufacturing plants in Europe, Boffetta et al. (2003)
reported results from 1348 personal exposure measurements of titanium dioxide dust that
were predominantly collected during routine measurement programmes. The results
related to inhalable, respirable and ‘total’ dust measurements, which were converted to
respirable dust levels using several conversion factors. To convert ‘total’ to inhalable dust,
TITANIUM DIOXIDE 207
a conversion factor of 1.2 was used, based on a study by Kenny et al. (1997). A factor of
0.3 was chosen to convert inhalable titanium dioxide dust measurements to respirable
measurements, based on results from a study in the European carbon black manufacturing
industry (Gardiner et al., 1992). Table 1.6 summarizes the results for these standardized
levels of respirable titanium dioxide for the packing areas in these plants. The highest
levels were observed in Factory 10, where the geometric mean (GM) respirable dust
levels ranged from 7.99 mg/m3 between 1970 and 1974 to approximately 1.3–2.2 mg/m3
between 1980 and 1999. The authors mentioned that one of the possible reasons for the
relatively high exposure levels in Factory 10 may reflect the conversion factors used
rather than actual differences in exposure, and care should be taken when interpreting the
differences in exposure between the factories.
Although not reported in the study by Boffetta et al. (2003, 2004), results from other
areas in the titanium dioxide plants were also obtained. Table 1.7 includes results from
inhalable and ‘total’ dust measurements that have been converted to respirable dust levels,
and should therefore be interpreted with some care. Highest levels of exposure to
respirable dust were found in the drying and milling (GM range, 0.19–2.12 mg/m3) and
packing (GM, 0.48–2.11 mg/m3) areas, although high exposure levels were also observed
for maintenance workers (GM, 0.62–2.24 mg/m3), handymen (GM, 4.02 mg/m3) and
cleaners (GM, 5.02 mg/m3). Exposure levels appear to have declined between 1970 and
2000, due to the implementation of control measures such as local exhaust ventilation,
increased automation and isolation or segregation of personnel (Sleeuwenhoek, 2005).
To enable a quantitative exposure–response analysis, exposure reconstruction was
undertaken for each occupational title at each plant for different time periods (Boffetta et
al., 2003, 2004) using a method developed by Cherrie et al. (1996). The yearly estimated
exposure to titanium dioxide dust by factory between 1950 and 1999 varied between
0.1 and 1.0 mg/m3 (Boffetta et al., 2004). However, very high exposure levels were
estimated (>7 mg/m3) in several factories either for cleaning jobs during the end of the
production process or for jobs that involved recycling of titanium dioxide dust. Jobs with
the highest estimated exposure to titanium dioxide were recycling/blending, sweeper,
cleaner, packing, drying, warehouseman and fitter/mechanic (Boffetta et al., 2003). The
authors observed a decreasing trend in exposure, particularly in factories with the highest
estimated exposures during the early production period. Although the highest exposure
levels in the factory were in the order of 1.0 mg/m3, average levels ranged up to
5.0 mg/m3 for individual occupational titles (Boffetta et al., 2004).
Somewhat higher exposure levels were found in earlier studies. Reported
concentrations of total dust ranged from 10 to 400 mg/m3 during the grinding of titanium
dioxide pigment, but documentation of these levels was not provided (Elo et al., 1972).
Long-term exposures to titanium dioxide dust in a titanium pigment production factory
occasionally exceeded 10 mg/m3, and exposures greater than 10 mg/m3 were common
during the repair of production machinery (Rode et al., 1981).
208 IARC MONOGRAPHS VOLUME 93
Table 1.5. Personal ‘total’ exposure to titanium dioxide in four titanium
dioxide manufacturing plants in the USA by job category (1976–2000)
Job category No. Mean
(mg/m3)
SD Median
(mg/m3)
GM
(mg/m3)
Packers, micronizers
and addbacks 686 6.2 9.4 3.0 2.7
Ore handlers 21 1.1 1.1 0.9 0.6
Maintenance
mechanics 59 2.5 6.9 0.7 0.7
Dry and wet
treatment 117 2.0 7.6 0.3 0.4
Other exposed jobs 31 0.6 0.9 0.4 0.4
Adapted from Fryzek et al. (2003)
GM, geometric mean; No., number of samples; SD, standard deviation
Table 1.6. Exposure to titanium dioxide in packing areas in titanium dioxide
manufacturing plants in Europe
Factory Year No. of measurements GM (mg/m3) Interquartile range Range
1 1995–99
2000–02
55
9
1.33
0.68
0.46–3.31
0.20–2.74
0.10–19.86
0.13–4.17
3 1990–94
1995–99
2000–02
1
61
6
0.25
0.88
0.69

0.50–1.90
0.27–1.75

0.04–7.74
0.27–3.83
6 1990–94
1995–99
6
13
1.24
2.51
0.61–2.47
1.63–4.31
0.47–5.14
0.72–9.72
8 1995–99 11 0.77 0.48–0.96 0.32–6.16
9 1985–89
1990–94
1995–99
12
16
18
1.57
2.00
1.31
0.96–2.44
1.44–3.08
0.80–1.99
0.72–4.64
0.64–3.39
0.40–4.24
10 1970–74
1975–79
1980–84
1985–89
1990–94
1995–99
10
20
22
18
19
6
7.99
2.49
2.16
1.31
1.34
2.11
3.64–16.64
1.64–3.53
1.25–3.88
0.94–1.93
0.94–2.23
1.60–3.28
2.34–79.20
1.01–6.41
0.63–10.91
0.68–5.04
0.32–5.29
0.47–3.96
15 1985–89
1990–94
1995–99
76
92
37
0.47
0.45
0.63
0.31–0.70
0.29–0.66
0.32–1.57
0.02–3.54
0.06–4.94
0.04–4.89
Adapted from Boffetta et al. (2003)
GM, geometric mean
TITANIUM DIOXIDE 209
Table 1.7. Measurements of respirable dust (mg/m3) from the white enda of
the titanium dioxide manufacturing process in Europe (1970–2000)
Area Plant No. GM Interquartile
range
Range
Moore filtration 1
8
8
8
0.11
0.28
0.06–0.54
0.16–0.64
<0.01–0.94
0.08–0.80
Calcination 10
15
28
4
0.78
1.01
0.36–1.25
0.40–3.18
0.18–4.79
0.39–3.68
Raymond mills and conveying 9 29 1.20 0.88–1.72 0.25–3.84
Surface treatment 1
15
59
5
0.66
0.10
0.29–1.31
0.04–0.37
0.05–17.30
0.04–0.57
Drying and milling 3
8
9
10
15
30
2
46
135
6
0.44
0.71
2.12
1.37
0.19
0.12–1.62

1.40–3.82
0.86–2.09
0.08–0.89
0.02–10.80
0.48–1.04
0.49–7.76
0.32–20.66
0.02–2.35
Packing 1
3
6
8
9
10
15
64
68
19
11
46
95
205
1.21
0.84
2.01
0.77
1.59
2.11
0.48
0.45–2.97
0.46–1.72
1.25–4.26
0.48–0.96
0.96–2.57
1.12–3.42
0.30–0.70
0.10–19.86
0.04–7.74
0.47–9.72
0.32–6.16
0.04–4.64
0.32–79.20
0.02–4.94
Warehouse 3
10
38
6
0.29
1.96
0.15–0.53
1.32–2.84
0.04–4.89
1.08–3.28
Forklift truck driver 15 12 0.45 0.24–0.97 0.14–2.14
Loader 15 13 0.29 0.15–0.35 0.10–4.98
Maintenance 1
3
10
32
28
47
0.62
0.97
2.24
0.14–1.59
0.33–2.79
1.30–3.38
0.04–9.07
0.04–18.86
0.54–10.19
White end 8 5 1.36 0.60–3.32 0.32–3.44
Handyman 10 44 4.02 2.54–7.35 0.72–20.16
Cleaner 10 9 5.02 3.40–8.71 1.15–9.68
Adapted from Sleeuwenhoek (2005)
GM, geometric mean
a White end, TiO2 precipitation and all subsequent processes
210 IARC MONOGRAPHS VOLUME 93
(b) Particle concentration
Wake et al. (2002) reported the results of measurements taken with a P-trak,
Portacount or scanning mobility particle sizer in a titanium dioxide manufacturing plant in
the United Kingdom. The particle number concentrations in the bagging area ranged
from 4.2 × 103 particles/cm3 to 16.6 × 103 particles/cm3 compared with 9.7–
58.4 × 103 particles/cm3 outside the plant on the same day, which indicated that
exposure to ultrafine particles (not in conglomerates) is relatively low. [The report does
not specify what method was used to count the airborne titanium dioxide particles or what
size particles were included in these measurements.]
Various other exposure concentrations have been reported in the manufacture of
titanium dioxide, such as ore and other dusts, sulfuric acid, sulfur dioxide, welding fumes,
hydrochloric acid and asbestos.
(c) User industries
Titanium dioxide is used in various industries (see Section 1.2.2) and exposure may
occur before and during the addition of titanium dioxide to matrices such as paints,
coatings, plastics, rubber, ink and foodstuffs. The potential for exposure is greatly reduced
in other parts of the process. Very little information is available on exposure to titanium
dioxide in various user industries.
In the pulp, paper and paper product industry, Kauppinen et al. (2002) estimated that
70% of stock preparation departments had an exposure prevalence greater than 5% (i.e.
more than 5% of the workforce was exposed); this proportion was 73% for on-machine
coating of paper. The median level of exposure in these departments was assessed to be
between 1.5 and 10 mg/m3.
No significant exposure to primary particles of titanium dioxide is thought to occur
during the use of products in which titanium dioxide is bound to other materials, such as
in paints.
1.3.3 Environmental exposure
No information was available to the Working Group on environmental exposure to
titanium dioxide.
1.4 Regulations and guidelines
Occupational exposure regulations and guidelines in several countries are presented in
Table 1.8.
Current occupational exposure limits for titanium dioxide in the USA are based on the
airborne mass fractions of either respirable or ‘total’ dust fractions, and may be the same
for titanium dioxide and particles that are not otherwise regulated or classified, with limits
ranging from 1.5 mg/m3 for respirable dust excluding ultrafine particles (Federal Republic
TITANIUM DIOXIDE 211
Table 1.8 Occupational exposure standards and guidelines for titanium dioxide
Country or region Concentration
(mg/m3)
Interpretation
Austria 6 TWA – ACC
Belgium 10 TWA – ACC
China 8 (T)
10 (T)
0 (T)
TWA
STEL
Ceiling
Canada
Alberta
British Columbia
Ontario
Quebec
10 (T)
3 (R)
10 (T)
20 (T)
10 (T)
10 (T)
TWA
TWA
TWA
STEL
TWA
TWA; containing no asbestos and < 1% crystalline silica
Czech Republic 10 TWA – ACC
Denmark 6 (as Ti) TWA
Finland 10 TWA
France 10 TWA
Germany 1.5a (R) MAK (see also aerosol allowable concentrations)
Greece 10 TWA – ACGIH (from ACC)
Hong Kong 3 (R)
10 (T)
TWA
TWA
Ireland 4 (R)
10 (I)
TWA
TWA
Italy 10 TWA – ACGIH (from ACC)
Mexico 10
20
TWA
STEL
Netherlands 10 (I)
5 (R)
TWA – ACC
TWA – ACC
New Zealand 10 (I) TWA; containing no asbestos and <1% free silica
Norway 5 TWA
Poland 10 (I) TWA; containing no asbestos and <2% free crystalline
silica
Portugal 10 TWA – ACGIH (from ACC)
South Africa 5 (R)
10 (I)
TWA
TWA
Spain 10 TWA
Sweden 5 (T) TWA
Switzerland 3 TWA
United Kingdom 4 (R) TWA
USA
ACGIH (TLV)
NIOSH (REL)
OSHA (PEL)
10 (A4)
(Ca)
15 (T)
TWA
lowest feasible concentration
TWA
From Direktoratet for Arbeidstilsynet (2002); SUVA (2003); American Chemistry Council (2003); ACGIH
Worldwide (2005); Deutsche Forschungsgemeinschaft (2005); Health and Safety Executive (2005); INRS
(2005); Työsuojelusäädöksiä (2005)
A4, not classifiable as a human carcinogen; ACC, American Chemistry Council; ACGIH, American Conference
of Government Industrial Hygienists; Ca, potential occupational carcinogen; I, inhalable dust; MAK, maximum
concentration at the workplace; NIOSH, National Institute of Occupational Health; OSHA, Occupational Safety
and Health Administration; PEL, permissible exposure limit; R, respirable dust; REL, recommended exposure
level; STEL, short-term exposure limit; T, total dust; TLV, threshold limit value; TWA, 8-h time-weighted
average
a Excluding ultrafine or aggregates of ultrafine
212 IARC MONOGRAPHS VOLUME 93
of Germany maximum concentration value in the workplace) to 15 mg/m3 for total dust
(Occupational Safety and Health Administration, 2002). The National Institute for
Occupational Safety and Health (NIOSH, 2005) currently has no recommended exposure
limit for titanium dioxide in the USA and classifies it as a potential occupational
carcinogen. [The Working Group is aware that the National Institute for Occupational
Health is considering recommending exposure limits of 1.5 mg/m3 for fine titanium
dioxide and 0.1 mg/m3 for ultrafine titanium dioxide as time-weighted average
concentrations for up to 10 hour per day during a 40-hour work week. This
recommendation would remove the current classification of titanium dioxide as an
occupational carcinogen.]
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Windholz M, ed (1983). The Merck Index, 10th Ed, Rahway, NJ, Merck, p.1356.

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