UCLA Study Reports Nanoparticle-Related Genetic Damage in Mice
January 24, 2010
LOS ANGELES - Titanium dioxide nanoparticles, found in everything from cosmetics and sunscreen to paint and vitamins, caused systemic genetic damage in mice, according to a comprehensive study conducted by researchers at UCLA's Jonsson Comprehensive Cancer Center. The study appears in the journal Cancer Research.
Titanium dioxide (TiO2) nanoparticles induced single- and double-strand DNA breaks and caused chromosomal damage, as well as inflammation, all of which increase the risk of cancer.
The UCLA study is the first to show that the nanoparticles had such an effect, said senior study author Robert Schiestl, UCLA Professor of Pathology, Radiation Oncology and Environmental Health Sciences and a Jonsson Cancer Center scientist.
Once in the body, the TiO2 nanoparticles accumulate in different organs because the body has no way to eliminate them. And because they are so small, they can go everywhere, even through cells, and may interfere with sub-cellular mechanisms.
In the past, these TiO2 nanoparticles have been considered nontoxic because they do not incite a chemical reaction. Rather, it is the surface interactions the nanoparticles have within their environment, in this case inside a mouse, that causes the genetic damage, Schiestl said. They wander throughout the body causing oxidative stress, which can lead to cell death.
It is a novel mechanism of toxicity, a physicochemical reaction, that these particles cause, in comparison to regular chemical toxins, which are the usual subjects of toxicological research, Schiestl said.
"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," Schiestl said. "This is the first comprehensive study of titanium dioxide nanoparticle–induced genotoxicity, possibly caused by a secondary mechanism associated with inflammation and/or oxidative stress. Given the growing use of these nanoparticles, these findings raise concern about potential health hazards associated with exposure."
In the study, mice were exposed to the TiO2 nanoparticles in their drinking water and began showing genetic damage on the fifth day. The human equivalent is about 1.6 years of exposure to the nanoparticles in a manufacturing environment. However, Schiestl said, it's not clear if regular, everyday exposure in humans increases exponentially as continued contact with the nanoparticles occurs over time.
"These data suggest that we should be concerned about a potential risk of cancer or genetic disorders, especially for people occupationally exposed to high concentrations of titanium dioxide nanoparticles, and that it might be prudent to limit their ingestion through non-essential drug additives, food colors, etc.," the study states.
Next, Schiestl and his team will study exposure to the nanoparticles in mice that are deficient in DNA repair, to perhaps help find a way to predict which people might be particularly sensitive to them.