Carbon Nanotube adverse effect

Carbon nanotubes are unique materials with specific properties [42]. There is a considerable application potential for using nanotubes in the biomedical field. However, when such materials are considered for application in biomedical implants, transport of medicines and vaccines or as biosensors, their biocompatibility needs to be established. Other carbon materials show remarkable long-term biocompatibility and biological action for use as medical devices. Preliminary data on biocompatibility of nanotubes and other novel nanostructured materials demonstrate that we have to pay attention to their possible adverse effects when then-biomedical applications are considered. 

The number of studies on the health effects of fullerenes and carbon nanotubes is rapidly increasing. However, the data on their toxicity are often mutually contradictory. For example, the researchers from universities of Rice and Georgia (USA) found that in aqueous fullerene solutions colloidal nano-C particles were formed, which even at low concentration (approximately 2 molecules of fullerene per 108 molecules of water) negatively influence the liver and skin cells [17-19]. The toxicity of this nano-C aqueous dispersion was comparable to that of dioxins. In another smdy, however, it was shown that fullerene had no adverse effects and, on the contrary, had anti-oxidant activity [20]. Solutions of prepared by a variety of methods up to 200 mg/mL were not cytotoxic to a number of cell types [21]. The contradiction between the data of different authors could be explained by different nano-C particles composition and dispersion used in research. 

EPA withdrew two of the SNURs because they were issued as direct final rules without following the notice and comment procedure for formal rule-making, and it received a notice that adverse comments would be submitted, but EPA proposed them again three months later. These two SNURs were for carbon nanotubes. While the carbon nanotube SNURs were in effect, the EPA received questions about whether they applied to all carbon nanotubes, or just the two specific carbon nanotubes that were listed in the SNUR. The EPA issued a clarification confirming that the SNURS, like all SNURS, only relate to the exact chemical substances named in the regulation, and not all nanotubes in general. The EPA reminded companies that any carbon nanotube that is not already on the Inventory must be put on the Inventory through the PMN process. It appears that EPA made this point because SNURs are not issued until a substance is on the Inventory and therefore a manufacturer of a different carbon nanotube that is not on the Inventory would have to comply with the PMN rules. 

As discussed in Chapter 6, the incorporation of reinforcing agents or fillers into plastic formulations can, in some but not all cases, lead to variations in the molecular stability of plastics and also their thermal and thermooxidation stability. Thus, it has been observed that the addition of silica to polytetrafluoroethylene did not adversely affect polymer stability, while the incorporation of 25% of organically modified silica into polyethylene led to a decrease in weight loss of the plastic from 80% to 33.7%. The incorporation of carbon nanotubes in epoxy resins unproved their mechanical and thermal properties. It is fair to say that the effect of reinforcing agents on the thermal and thermooxidative stability of polymers must always be bom in mind when selecting polymer formulations for a particular application. 

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