Wednesday, June 21, 2006

Who’s afraid of nanoparticles?

Lots of people, it seems. They have the potential to become the new DDT or dioxins or hormone mimics, the invisible ingredients of our environment and our synthetic products that are suspected of wreaking biochemical havoc. I don’t say the notion is ridiculous, but we need to keep it in proportion. The Royal Society/RAE report on the hazards and ethics of nanotechnology did a good job of giving some perspective on the concerns: we shouldn’t take it for granted that nanoparticles are safe (even if their bulkier counterparts are), but neither are we totally ignorant about exposure to such particles, and it is unlikely that we can make many generalizations about their health risks. Certainly, we need legislation to stop these tiny grains from slipping through current health & safety regulations.

My recent article on the damaging effects that titania nanoparticles apparently have on mouse microglia, the defensive cells of the brain, will probably be welcomed as ammunition by those who want a moratorium on all nanoparticle research. It does not give grounds for that – this research is a long way from establishing actual neurotoxocity – but it does give pause for thought about nanoparticle sun creams. I rather suspect this stuff is not going to be a major hazard, but we can’t be sure of that, and I confess that I’ll prefer to avoid them this summer.

For various mundane reasons, some comments by the EPA researchers involved in this work didn’t make it into the article. But they help to put the implications in perspective, and so I’m posting them here:
Responses from Dr. Bellina Veronesi
Question: Apart from sun creams, which consumer products that involve contact with the human body currently use titania nanoparticles?
Answer: Cosmetics, prosthetics (artificial joints, for example)
Question: You mention toothpaste and cosmetics - do you know of specific examples of these?
Answer: Most product labels would probably not note if a given chemical concentration was in the “nano” range. Often times, the titanium oxide is listed in the ingredients, but is not identified as "nano-." More specific information might be considered to be confidential business information (CBI) and not available.
Question: I'm finding it hard to see from the paper exactly how long the production of ROS tended to continue for after the microglia were exposed.
Answer: Over a 120 minute period, which was the extent of our measurements.
Question: It seems that the worry is not about the response per se, but that it is sustained.
Answer: The concern from the neurobiology/neurotoxicology point of view is that a cell type (the microglia), whose job it is to react to offending foreign stimuli in the brain by releasing free radicals (ROS), is doing just that in response to nanosize Titanium dioxide. If those free radicals are not neutralized by anti-oxidants present in the brain (Vitamin C, Vitamin E, super oxide dismutase), they can damage neurons.
But remember, these measurements were made in isolated microglia, so we can't yet say if it is neurotoxic. Rather, the next step would be to examine the consequences of ROS release in a more complex culture system consisting of mixtures of brain cells, including microglia and neurons. Based on those findings, we would then test in animals.
Question: What do we know about how such nanoparticles might get transported around the body? Can you say anything about the chances of them reaching the brain?
Answer: Experts such as Dr. Wolfgang Kreyling (GSF Institute for Inhalation Biology (Munich)) have shown that nanosize particles, such as TiO2, can leave the lungs of exposed animals and distribute to other organs. However, it is still undetermined whether TiO2 can cross the blood brain barrier and enter the brain.
Question: Can you say anything about whether the concentrations you studied might be realistic in terms of exposure levels?
Answer: It is not “good science” to extrapolate in vitro data to whole animal/human response. There are many obligatory steps/test models that must be tested first. Similarly, our study was not designed to assess whether the test concentrations used in the cell culture studies have relevance to those found in consumer products.
Question: How worrying are the results at this point, given that they are not in vivo studies?
Answer: This was a carefully designed study that followed a format prescribed in the nanoparticle scientific literature ((Nel et al., Science 2006) That format entails moving from cell culture to animal testing in a tiered fashion. We are examining further the possibility that TiO2 may be neurotoxic in culture. If these results prove positive, we will adhere to the format and next test in more complex culture models that use neurons or dissociated whole brain to determine. Results of these studies will determine if animal studies should be pursued.
Question: What are the major uncertainties about how the findings might translate to humans, and what are the next steps?
Answer: This study exposed TiO2 to isolated, brain cells taken from a mouse. Within the confines of this model, it would be speculative to say what the effects would occur in human cells, let alone a human being. Such a prediction requires an extremely lengthy course of testing, involving successively more complicated experimental models. As I noted in my previous answer, we will follow a format that allows for such sequential research.
Question: How do you feel about the fact that titania nanoparticles are currently in use in consumer products? Would you want to use such products yourself?
Answer: Nano-size TiO2 has been in commercial use/multiple routes of human exposure for several years, providing great benefits without incident. Numerous already published studies give TiO2 (nanosize, larger size) a clean bill of health.
The uniqueness of this study is that we are looking at the response of cells with very high resolution, state-of-the-art measurements. Again, this is the initial stage of a very lengthy experimental process the findings of which will provide better insight and guidance related to the use of such products.


Ronan Jimson said...

Great Work!!!
this is a good link you can refer Art Collection

Anonymous said...

歐美a免費線上看,熊貓貼圖區,ec成人,聊天室080,aaa片免費看短片,dodo豆豆聊天室,一對一電話視訊聊天,自拍圖片集,走光露點,123456免費電影,本土自拍,美女裸體寫真,影片轉檔程式,成人視訊聊天,貼圖俱樂部,辣妹自拍影片,自拍電影免費下載,電話辣妹視訊,情色自拍貼圖,卡通做愛影片下載,日本辣妹自拍全裸,美女裸體模特兒,showlive影音聊天網,日本美女寫真,色情網,台灣自拍貼圖,情色貼圖貼片,百分百成人圖片 ,情色網站,a片網站,ukiss聊天室,卡通成人網,3級女星寫真,080 苗栗人聊天室,成人情色小說,免費成人片觀賞,

傑克論壇,維納斯成人用品,免費漫畫,內衣廣告美女,免費成人影城,a漫,國中女孩寫真自拍照片,ut男同志聊天室,女優,網友自拍,aa片免費看影片,玩美女人短片試看片,草莓論壇,kiss911貼圖片區,免費電影,免費成人,歐美 性感 美女 桌布,視訊交友高雄網,工藤靜香寫真集,金瓶梅免費影片,成人圖片 ,女明星裸體寫真,台灣處女貼圖貼片區,成人小遊戲,布蘭妮貼圖片區,美女視訊聊天,免費情色卡通短片,免費av18禁影片,小高聊天室,小老鼠論壇,免費a長片線上看,真愛love777聊天室,聊天ukiss,情色自拍貼圖,寵物女孩自拍網,免費a片下載,日本情色寫真,美女內衣秀,色情網,

Anonymous said...


女優王國,免費無碼a片,0800a片區,免費線上遊戲,無名正妹牆,成人圖片,寫真美女,av1688影音娛樂網,dodo豆豆聊天室,網拍模特兒,成人文學,免費試看a片,a片免費看,成人情色小說,美腿絲襪,影片下載,美女a片,人體寫真模特兒,熊貓成人貼,kiss情色,美女遊戲區,104 貼圖區,線上看,aaa片免費看影片,天堂情色,躺伯虎聊天室,洪爺情色網,kiss情色網,貼影區,雄貓貼圖,080苗栗人聊天室,都都成人站,尋夢園聊天室,a片線上觀看,無碼影片,情慾自拍,免費成人片,影音城論壇,情色成人,最新免費線上遊戲,a383影音城,美腿,色情寫真,xxx383成人視訊,視訊交友90739,av女優影片,