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And in research in his labs, in which mice are not injected with nanotubes but breathe it into their lungs -- the way people would presumably be exposed -- the animals developed inflammation that peaked within seven days of exposure, and returned to normal within one or two months. "Whether the material is asbestos-like is still a question to be debated," Castranova said. "Having a panic that you have the next asbestos is a little bit premature in my view." It's also worth noting that the new study did not find an asbestos-like effect with shorter or more tangled strands of carbon nanotubes. That does not mean smaller carbon nanotubes are necessarily safe. It just means that the asbestos-like effects in this experiment did not come from inherent properties of all carbon nanotubes. Rather, those effects came from stacking nanotubes together into a long, thin, asbestos-like fiber, which the body struggles to process. Carbon nanotubes basically are minuscule, rolled pipes of graphite. They can be as narrow as one nanometer, or one billionth of a meter. (For comparison, a human hair is more than 80,000 nanometers across.) Because their structure endows them with powerful physical properties, such as strength greater than that of steel, carbon nanotubes are being explored for a wide range of uses in electronics and medicine. Some potential applications involve coating the nanotubes in other substances, which could blunt any toxic effects. For example, researchers have explored using nanotubes as the mechanism for delivering tiny, cancer-killing smart bombs to tumors. Stanford University scientists involved in such work found that coated, short carbon nanotubes -- unlike the ones at issue in the asbestos study -- were safely digested by mice after being injected into their bloodstreams. Maynard said the combination of that research with his group's new study "shows there are no simple answers here. What type of materials you're using and what you're using them for makes a big difference." Related Links: Eric Bland's blog: What the Tech? How Stuff Works: Carbon Nanotubes Oak Ridge National Laboratory's Nanomaterials Synthesis and Properties Group |
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