Titanium dioxide (TiO2) nanoparticles, found in everything from cosmetics
to sunscreen to paint to vitamins, caused systemic genetic damage in mice, according
to a comprehensive study conducted by researchers at UCLA's
Jonsson Comprehensive Cancer Center.
The TiO2 nanoparticles induced single- and double-strand DNA breaks and also
caused chromosomal damage as well as inflammation, all of which increase the
risk for cancer. The UCLA study is the first to show that the nanoparticles
had such an effect, said Robert Schiestl, a professor of pathology, radiation
oncology and environmental health sciences, a Jonsson Cancer Center scientist
and the study's senior author.
Once in the system, 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 in the body, even through cells, and may interfere with sub-cellular
mechanisms.
The study appears this week in the journal Cancer Research.
In the past, these TiO2 nanoparticles have been considered non-toxic in that
they do not incite a chemical reaction. Instead, it is surface interactions
that the nanoparticles have within their environment- in this case inside a
mouse - that is causing 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, 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," he 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."
The manufacture of TiO2 nanoparticles is a huge industry, Schiestl said, with
production at about two million tons per year. In addition to paint, cosmetics,
sunscreen and vitamins, the nanoparticles can be found in toothpaste, food colorants,
nutritional supplements and hundreds of other personal care products.
"It could be that a certain portion of spontaneous cancers are due to
this exposure," Schiestl said. "And some people could be more sensitive
to nanoparticles exposure than others. "I believe the toxicity of these
nanoparticles has not been studied enough."
Schiestl said the nanoparticles cannot go through skin, so he recommends using
a lotion sunscreen. Spray-on sunscreens could potentially be inhaled and the
nanoparticles can become lodged in the lungs.
The 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.
The study was funded by the National Institutes of Health.
Posted November 16th, 2009
