19 November 2009

Sunscreen, cosmetics cause DNA damage

by Kate Melville

Titanium dioxide (TiO2) nanoparticles - ubiquitous in common household products such as cosmetics, sunscreen and vitamins - cause systemic genetic damage in mice, according to a new study by researchers at UCLA's Jonsson Comprehensive Cancer Center.

Senior author of the study, Robert Schiestl, said the 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.

The study, published in Cancer Research, explains that the TiO2 nanoparticles accumulate in different organs because the body has no effective way to eliminate them. And because they are so small, they can go everywhere in the body, even through cells, where they may even interfere with sub-cellular mechanisms.

In the past, such nanoparticles were considered non-toxic because they did not incite a chemical reaction. But the researchers point out that it is the surface interactions that the nanoparticles have within their environment - in this case inside a mouse - that causes the genetic damage. This mechanism of toxicity is known as a physicochemical reaction.

"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," said Schiestl. "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, 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 speculated. "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 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. He also pointed out that the nanoparticles cannot go through skin, so a lotion sunscreen is a safer option than spray-on sunscreens, which could be inhaled and become lodged in the lungs.

Brain can "tidy-up" nanojunk, say Swedish boffins
Nanoparticle Laced Wastewater Could Compromise Treatment Plants
From Little Things, Big Conundrums Grow
Size matters! Nanosilver risks unknown, says industry watchdog

Source: University of California - Los Angeles