The researchers at the University of California, Los Angeles, arrived at this conclusion following a mouse study that suggested ingestion of the nanoparticles led to genetic damage.
In addition to warning against occupational exposure, the study, published in the journal of Cancer Research, warns against the ingestion of food colours, vitamins and non essential drug additives that contain titanium dioxide nanoparticles.
One of the study’s authors Dr Robert Schiestl also advised against using spray-on sunscreens as these could lead to the inhalation of titanium dioxide nanoparticles that are often used to improve the UV protection provided by the products.
Sticking to sun protection products in cream or lotion form is preferable as the nanoparticles don’t cross the skin barrier, according to Schiestl.
The UCLA study looked at the effects of feeding mice titanium dioxide nanoparticles in their daily water supply for a period of five days for adult males, and ten days for pregnant females from day 8.5 to day 18.5 post coitum.
Effects on the DNA and genetic material of the mice were observed to investigate whether ingesting the nanoparticles was genotoxic, led to DNA damage and brought on an inflammatory response within the organism.
According to the study, exposure to titanium dioxide nanoparticles leads to double strand DNA breaks in the mice, in a dose dependent manner - the higher the dose of titanium dioxide the higher the number of double strand breaks.
The double strand DNA breaks are particularly important in a health context as they are more damaging than single strand breaks or oxidative damage, which are transient, according to the authors.
In pregnant females, exposure to the nanoparticles induced significantly more DNA deletions in their offspring than those not exposed.
Inflammatory mechanism
The team also found higher concentrations of markers of inflammation and oxidative stress in the mice that had been exposed to the titanium dioxide nanoparticles, which led the researchers to suggest the toxicity of the particles could be due to their ability to elicit an inflammatory response.
Explaining the potential mechanism, Schiestl said in a statement: “The novel principle is that titanium by itself is chemically inert. However, when the particles become progressively smaller, their surface, in turn, becomes progressively bigger and in the interaction of this surface with the environment, oxidative stress is induced.”
Further human studies are needed in order to truly understand the health effects of titanium dioxide nanoparticles, but the researchers feel the data suggests we should be ‘concerned’ about cancer or genetic disorders for those working with the material and that it would be ‘prudent’ to limit the ingestion of the materials.
“It could be that a certain portion of spontaneous cancers are due to this exposure. And some people could be more sensitive to nanoparticles exposure than others. I believe the toxicity of these nanoparticles has not been studied enough,” added Schiestl.
Source: Journal of Cancer Research
2009, volume 69, issue 22
Titanium Dioxide Nanoparticles Induce DNA Damage and Genetic Instability in vivo in Mice
Benedicte Trouiller, Ramune Reliene, Aya Westbrook, Parrisa Solaimani, Robert H. Schiestl