CNT-asbestos links point to need for more research, say experts

by James Montgomery, News Editor, Solid State Technology

May 22, 2008 – A new report published in the journal Nature Nanotechnologies is raising alarms about apparent health risks associated with carbon nanotubes (CNT), similar to those seen with asbestos. But efforts are already underway to look more closely at potential issues, according to Walt Trybula, former SEMATECH immersion lithography guru and now at Texas State, in an email exchange with WaferNEWS.

The Nature Nanotechnology report concludes that the needle-like fiber shape of CNTs resembles that of asbestos, and researchers in the UK cited their work showing that exposing the mesothelial lining of a mouse to long multiwalled CNTs “results in asbestos-like, length-dependent, pathogenic behavior,” including formation of lesions. The scientists claim that the results cast doubt whether CNTs are “no more hazardous than graphite,” and urge for more research “and great caution before introducing such products into the market.”

The International Council on Nanotechnology (ICON) released a statement commenting on the study (and a previous one published in the Journal of Toxicological Sciences), noting that the work doesn’t address whether humans can be exposed to the CNTs in a way to cause mesothelioma. Questions remain, said ICON: what are the correlative factors to humans vs. mice — e.g., in terms of CNT exposure/dosage, if the CNTs stay in the body long enough to have the same impact, whether there’s a difference between long and short-length CNTs or if nonfibrous tangled CNTs have the same effect, whether iron in the samples was in fact the agent responsible, etc.

Trybula told WaferNEWS that among the various types of asbestos, Crocidolite is the most dangerous, with a shape consisting of straight needle-like fibers. However, he pointed out, some experts suggest only lengths of >5μm are of concern, and in these experiments bundles of 20μm CNTs were the culprit. And, he said, some reports have noted the CNT doses in the UK study “were extremely high” — and he added that massive amounts of ordinary drinking water, too, can be fatal.

But the issue of widening the known health/safety impact of CNTs and other new nanotechnologies is a real one. “We know there are potential issues,” said Trybula. “We need to understand and address the problems.” He noted that there have been some cases where people showed or exposed problems with nanotechnology and didn’t follow up to help with answers or suggestions. “We need to have people that will fix the problem.”

Trybula, now director of the Nanomaterials Application Center (NAC) at Texas State University-San Marcos, is working to help create a “Nano-Safety” program, which has a white paper about this issue that he said had been distributed to members of Congress. (Note: the group’s branding is to capitalize the name as NANO-SAFETY, “because there is nothing small” about the issue). NAC also is working with local firm nanoTox, which he says is working on nanotoxicological tests and safety screening technology.

The NAC currently is participating in a joint “nano-safety” education effort with Sam Houston State U., with another joint effort launching later this year with Sul Ross State U. “We are pushing this effort to educate people and train them in handling the developing nanotechnology products,” he said. “This needs to be a systematic solution.” — J.M.


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