티타늄 독성의 새로운 기작 밝혀져

티타늄 독성의 새로운 기작 밝혀져

가정에서 흔히 쓰이는 물품들에 있는 나노입자에 대한 새로운 점들이 밝혀졌다. 화장품에서 태양빛 차단품에 이르기까지 흔하게 쓰이는 티타늄 이산화물 (Titanium dioxide) 나노입자가 쥐에 유전독성을 일으킨다는 사실이 미국 캘리포니아 대학 (UCLA) 연구진에 의해 밝혀진 것이다.

또 이 연구진은 사상 최초로 티타늄 이산화물 나노입자들이 단일 또는 이중 나선 DNA 를 파괴하고 염증 뿐 아니라 염색체 파괴를 가져와 암에 대한 위험을 높인다는 것을 실증했다. 이 연구결과는 Cancer Research 지에 11월 16일경 발표되었다.

일단 몸 안에 들어오면 티타늄 이산화물들은 여러 장기들에 축적된다. 왜냐하면 몸이 이들을 제거할 방법이 없기 때문이다. 그리고 이들 입자들이 워낙 작아서 세포들을 포함해 몸 안 어디로든지 갈 수 있다. 그래서 세포 안쪽에서의 정상적인 기작을 방해할 수도 있는 것이다.

과거에는 이러한 티타늄 이산화물 나노입자들이 화학반응을 일으키지 않는다는 점에서 무독하다고 여겨져 왔다. 하지만 Schiestl 교수에 따르면 나노입자들 표면에서의 (이번 연구의 경우는 쥐 안에서) 상호작용으로 인해 유전독성을 일으킬 수 있다는 점이 이번 연구로 인해 새롭게 밝혀졌다. 이들 입자들은 세포 사멸을 불러오는 산화 스트레스를 몸 안을 돌아다니며 일으킨다. 이는 독성학연구에 있어서 일반적인 화학독성물질과는 다른 새로운 독성기작, 즉 물리화학적 반응을 갖는 것이다.

"새롭게 알아낸 또 하나는 티타늄 그 자체로만은 화학적으로 불활성이라는 점이다. 하지만 입자들이 점점 더 작아질 때 이들의 표면적은 점점 더 커진다. 즉 이 표면과 환경의 산화적 스트레스간의 상호작용이 생기게 되는 것이다.

이번 연구는 티타늄 이산화물 나노입자에 의해 생기는 유전독성에 관한 최초의 포괄적 연구이다. 이 독성은 염증 및 산화적 스트레스와 연관된 2차적 기작에 의해 생기는 것으로 보인다. 이들 나노입자들의 늘어만 가는 사용 정도를 볼 때 이번 발견들은 입자들에 노출되었을 시 생길 수 있는 가능한 인체 유해성에 대해 경종을 울릴 것으로 보인다." 라고 Schiestl 교수는 말했다.

티타늄 이산화물이 있는 제품들

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Nanoparticles Used in Common Household Items
Cause Genetic Damage in Mice

Titanium dioxide (TiO2) nanoparticles, found in everything from cosmetics to sunscreen to paint to vitamins, caused systemic genetic damage in mice. (Credit: iStockphoto)

ScienceDaily (Nov. 17, 2009) — 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 appeared the week of November 16 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.

Source : KISTI, sciencedaily.com