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Posted: August 15, 2007
Is fullerene toxicity a myth?
(Nanowerk News) In 2004 to 2005, a series of articles was published by different authors about fullerene toxicity, the series being initiated with reports by E. Obersdorster from Dallas University (USA) and V. Colvin from Rice University. It was noted in particular that the fish swimming in the water with the fullerene solution added into it experiences changes in the brain structure, and human skin cells die upon contact with the fullerene solution. These data allowed the authors of the articles to draw attention to environmental consequences of applying nanotechnologies, where fullerenes are of great importance. Apparently, once these technologies are eventually applied in industry, waste products will appear that contain such nanoparticles. The question arises as to how strict the requirements to such wastes should be?
The Kharkov researchers guided by G.V. Andrievsky, Ph. D. (Chemistry), called in question validity of fullerene apprehension. “We have been dealing with the fullerene aqueous solutions for more than ten years, and so far noticed no irritant impact on the skin. Moreover, aqueous solutions of pure fullerenes (i.e., no functional groups are attached to their surface) have positive biological effect and act as antioxidants.
Modified fullerenes can certainly be toxic, but this is the way functional groups’ characteristics become apparent, but not the properties of the fullerene per se, explained G.V. Andrievsky at the 8th International Conference “Fullerenes and Atomic Clusters” that took place in St. Petersburg early in July 2007. Besides, several articles were published within 2006, including the ones by E. Obersdorster, to describe recurrent experiments where toxicity effect had not been recorded.”
Where can a mistake be? The point is in the method for the fullerene aqueous solutions preparation. To prepare the solution, fullerenes are first dissolved in the polar solvent, which itself well dissolves in water. For example, the American researchers used tetrahydrofurane. It is impossible to refine the fullerene aqueous solution obtained in such a way from an organic solvent. It was the organic solvent that caused fish poisoning. “It is very strange that there occur negative changes in the fish brain, as no such changes are observed either in the liver or gills. Furthermore, lipid peroxygenation in these organs turned out to be slowed, that is fullerenes demonstrated their antioxidant properties. Selective brain lesions can be caused by substances like inhalation narcotics. One of them is the diethyl ether.
Tetrahydrofurane possesses the effect similar to that of the ether, but it is much more poisonous. It is tetrahydrofurane but not fullerenes that caused fish brain lesion. This model describes well the data available on toxicity of the fullerene aqueous solutions, says G.V. Andrievsky. We believe that non-modified fullerenes pose no hazard to the environment and they can be dealt with in the same way as ordinary soot.”