Titanium dioxide nanoparticle
[3] Surfaces of ultrafine titanium dioxide in the anatase structure have photocatalytic sterilizing properties, which make it useful as an additive in construction materials, for example in antifogging coatings and self-cleaning windows.
In the context of TiO2 production workers, inhalation exposure potentially presents a lung cancer risk, and standard hazard controls for nanomaterials are relevant for TiO2 nanoparticles.
In the chloride process, natural or synthetic rutile is chlorinated at temperatures of 850–1000 °C, and the titanium tetrachloride is converted to the ultrafine anatase form by vapor-phase oxidation.
This is in contrast to fine TiO2 (which has particle sizes below ~4 μm), which had insufficient evidence to classify as a potential occupational carcinogen, and has a higher recommended exposure limit of 2.4 mg/m3.
The lung tumor response observed in rats exposed to ultrafine TiO2 resulted from a secondary genotoxic mechanism related to the physical form of the inhaled particle, such as its surface area, rather than to the chemical compound itself, although there was insufficient evidence to corroborate this in humans.
[6]: 73–78 In addition, if it were combustible, when finely dispersed in the air and in contact with a sufficiently strong ignition source, TiO2 nanoparticles may present a dust explosion hazard.
[6]: 82 Elimination and substitution, the most desirable approaches to hazard control, may be possible through choosing properties of the particle such as size, shape, functionalization, and agglomeration/aggregation state to improve their toxicological properties while retaining the desired functionality,[19] or by replacing a dry powder with a slurry or suspension in a liquid solvent to reduce dust exposure.
[18] Administrative controls include training on best practices for safe handling, storage, and disposal of nanomaterials, proper labeling and warning signage, and encouraging a general safety culture.
[20] Personal protective equipment normally used for typical chemicals are also appropriate for nanomaterials, including long pants, long-sleeve shirts, closed-toed shoes, safety gloves, goggles, and impervious laboratory coats,[18] and in some circumstances respirators may be used.
[16] The U.S. Environmental Protection Agency generally does not consider physical properties such as particle size in classifying substances, and regulates TiO2 nanoparticles identically to other forms of TiO2.
[22] ISO/TS 11937 is a metrology standard for measuring several characteristics of dry titanium dioxide powder relevant for nanotechnology: crystal structure and anatase–rutile ratio can be measured using X-ray diffraction, average particle and crystallite sizes using X-ray diffraction or transmission electron microscopy, and specific surface area using the Brunauer–Emmet–Teller gas adsorption method.
It is intended as a benchmark in environmental or toxicological studies, and for calibrating instruments that measure specific surface area of nanomaterials by the Brunauer–Emmet–Teller method.
