Health and Safety
Titanium dioxide is incompatible with strong reducing agents and strong acids. Violent or incandescent reactions occur with molten metals that are very electropositive, e.g. aluminium, calcium, magnesium, potassium, sodium, zinc and lithium.
Titanium dioxide accounts for 70% of the total production volume of pigments worldwide. It is widely used to provide whiteness and opacity to products such as paints, plastics, papers, inks, foods, and toothpastes. It is also used in cosmetic and skin care products, and it is present in almost every sunblock, where it helps protect the skin from ultraviolet light.
Many sunscreens use nanoparticle titanium dioxide (along with nanoparticle zinc oxide) which does get absorbed into the skin. The effects on human health are not yet well understood. Nevertheless, allergy to topical application has been confirmed.
Titanium dioxide dust, when inhaled, has been classified by the International Agency for Research on Cancer (IARC) as an IARC Group 2B carcinogen, meaning it is possibly carcinogenic to humans. The findings of the IARC are based on the discovery that high concentrations of pigment-grade (powdered) and ultrafine titanium dioxide dust caused respiratory tract cancer in rats exposed by inhalation and intratracheal instillation. The series of biological events or steps that produce the rat lung cancers (e.g. particle deposition, impaired lung clearance, cell injury, fibrosis, mutations and ultimately cancer) have also been seen in people working in dusty environments. Therefore, the observations of cancer in animals were considered, by IARC, as relevant to people doing jobs with exposures to titanium dioxide dust. For example, titanium dioxide production workers may be exposed to high dust concentrations during packing, milling, site cleaning and maintenance, if there are insufficient dust control measures in place. However, the human studies conducted so far do not suggest an association between occupational exposure to titanium dioxide and an increased risk for cancer. The safety of the use of nano-particle sized titanium dioxide, which can penetrate the body and reach internal organs, has been criticized. Studies have also found that titanium dioxide nanoparticles cause inflammatory response and genetic damage in mice. There is some evidence the rare disease Yellow nail syndrome may be caused by titanium, either implanted for medical reasons or through eating various foods containing titanium dioxide.
Bundschuh et al. from the University Koblenz-Landau have found that waterflea (or daphnia) (a common test for mutagenicity) is damaged into the second generation when swimming in Water containing TiO2 nanoparticles.
The molecular mechanism by which TiO2 induces cancer is unclear. In 2012, Yanglong Zhu, John W. Eaton and Chi Li, on the basis of molecular research, suggested that cell cytotoxicity due to TiO2 results from the interaction between TiO2 nanoparticles and the lysosomal compartment, i.e., independently of the known apoptotic signalling pathways.
Read more about this topic: Titanium Dioxide
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