What is ultrafine or nanoparticulate titanium dioxide?
Titanium dioxide (TiO₂) is a white inorganic substance that is thermally stable, non-flammable, and insoluble. TiO₂, the oxide of the metal titanium which is the ninth most abundant element in the earth’s crust, occurs in many rocks and mineral sands, the most economically important being ilmenite and rutile deposits.
Although there are a number of definitions of “nanoparticulate” or “nanoparticle”, primary particles of ultrafine (UF) TiO₂ typically range in size from 10 to 60 nm and accordingly it meets most definitions of a nanomaterial. It should be stressed that “nanomaterial” is a categorization of a material by the size of its constituent parts. It neither implies a specific risk nor does it necessarily mean that this material actually has new hazard properties compared to its constituent parts. UF TiO₂ does not exist as discreet primary particles but as aggregates or agglomerates, with secondary particle sizes typically >100 nm. These aggregates do not readily break down into the individual nanoparticulate primary particles - either during processing, industrial use or in biological systems.
How much UF TiO₂ is produced annually?
At present, UF TiO₂ production accounts for approximately 1% of the total TiO₂ worldwide production or 50,000 ton in 2010.
What are the uses and benefits of UF TiO₂?
When well dispersed, UF TiO₂ is able to transmit visible light thus appearing transparent while also absorbing UV light, thus making it an excellent UV protector in sun-screen applications and as an industrial UV absorber. It has photocatalytic properties, making it a powerful catalyst to convert harmful species, such as NOx, SOx and VOC, into harmless by-products. In the last 25 years, UF TiO₂ has found increasing use in thermal catalysis as a pollution degrading catalyst used in fossil-fuel run power plants or in diesel engine exhausts where it has largely contributed to the decrease of NOx emissions. It also finds uses in the manufacture of high performance and miniaturized electronic components used in computers and other everyday life electronic devices.
Are there human health concerns with UF TiO₂?
Based on all of the human data collected to date, UF TiO₂ manufactured by Cristal and sold into current end uses approved by Cristal is safe.
TiO₂ can be present in the workplace as a dust or poorly soluble particle . However, since its introduction in 1923, there have been no significant health concerns associated with TiO₂ exposures. In 2006, the International Agency for Research on Cancer (IARC) reviewed the carcinogenic risk of TiO₂ concluding that it is “possibly carcinogenic to humans” (Group 2B) based primarily on studies in rats indicating lung tumors. However, the results from four large human epidemiology studies involving more than 20,000 workers in the titanium dioxide industry at manufacturing locations in North America and Europe indicate neither association with an increased risk of lung cancer nor with any other adverse lung effects.
Inhalation exposures to TiO₂ in rats can result in lung effects and lung tumors. It is generally recognized that the rat is uniquely sensitive to the effects of “lung overload”, with the production of chronic lung inflammation and subsequent lung fibrosis and tumor formation; a process not observed in other species including humans. The IARC conclusion was based on studies that involved rat “lung overload” effects.
In recent years, a number of publications have appeared linking potentially adverse effects from exposure to UF TiO₂. Most such studies employ unconventional testing methods and suffer from a number of other deficiencies including: the inappropriate use of large or exaggerated particle doses, having little or no relevance to human exposures; absence of appropriate positive and negative controls; and failures to demonstrate dose-response relationships.
Ultrafine forms of TiO₂ are not classified in the European Union as dangerous under either the Dangerous Substance Directive (EU Directive 67/548/EEC) or the more recent Classification Labeling and Packaging (CLP) Regulation (Regulation (EC) 1272/2008).
Evidence available at this time supports the safe manufacture and use of UF TiO₂ in current applications.
Are there environmental concerns with UF TiO₂?
Available information for UF TiO₂ indicates a low concern for environmental effects. Well-conducted studies following recognized international protocols indicate a low level of acute aquatic toxicity for UF TiO₂. Some few recent studies have reported chronic toxicity effects for UF TiO₂ in the aquatic environment. Given the insoluble nature of UF TiO₂, and its tendency to agglomerate and adhere to other particulates, the relevance of such studies, conducted in pure water and without the presence of sediment, is questionable.
What product stewardship measures are employed by Cristal for UF TiO₂?
As part of Cristal continuing commitment to product excellence, teams of experts conduct in-depth risk assessments of new and existing products. Cristal also plays leadership roles in industry associations such as the European Titanium Dioxide Manufacturers’ Association and the North American Titanium Dioxide Stewardship Council, with the goal of developing and sharing best practice on the safe use and sustainability of UF TiO₂ products.
Cristal is participating in the Organisation for Economic Cooperation and Development (OECD) Working Party on Manufactured Nanomaterials (WPMN) which was established in 2006. Work from this program continues with a number of advances recorded including the review and validation of appropriate testing methodologies and the development of appropriate analytical methodologies allowing accurate characterization and measurement of the nanoparticulate materials in the test systems. Such results will help direct future efforts for product characterization and for hazard and risk characterization of UF TiO₂.
Well conducted studies in animals employing routes of exposure and exposure levels relevant to human exposures, as well as large epidemiology studies conducted in exposed workers, indicate a low level of concern for UF TiO₂ exposures. Cristal safely produces UF TiO₂ and sells UF products only into select applications intended for industrial use.
The information provided herein is advisory only and have been promulgated solely as an illustrative example of certain health and safety practices that may be utilized to minimize exposure to ultrafine TiO2 during its handling and use. Thus, this information should be regarded as a guide that the user may or may not choose to adopt, modify or reject. This information does not constitute a comprehensive or complete analysis and should not be relied upon as such. The user is responsible to determine and implement appropriate exposure control to assure safe handling and use. Cristal specifically disclaims all warranties, express or limited, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose, or any warranty otherwise arising out of any proposal, specification, or sample. Cristal makes no warranties regarding the completeness, accuracy, reliability, applicability or availability of the information contained herein. In no event shall Cristal be liable for any damages, including without limitation, direct, indirect, special, exemplary or consequential damages, including lost profits, arising under the use of or reliance on information contained herein based in contract, negligence, strict liability, or otherwise, whether or not Cristal had any knowledge, actual or constructive, that such damages might be incurred. Additionally, Cristal shall not be liable in tort, contract, or otherwise, whether based in warranty, negligence, strict liability, or any other theory of liability for any action or failure to act in connection with the information contained herein, it being the user’s intent and understanding to absolve and to protect Cristal, its successors, assigns, principals and employees from any and all liability in tort, contract or otherwise.
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