Nanotubes and the tale of the rats

This Reuters report on how nanotubes will kill you (if you're a rat) was a prelude to Nanotox 2004 next week in the U.K. The news conference was a way to generate some media buzz in advance and get reporters all jazzed up over an event at the Royal Microscopical Society. Of course, Small Times' man in London will be there, so you can expect some first-rate reporting, with proper context.

The British scientists, meanwhile, were telling rat tales, pointing to DuPont toxicologist David Warheit's recent study on the toxicity of single-wall carbon nanotubes in rats.

Yes, it's DuPont that did the study, so you can read what you want into it, but the Center for Biological and Environmental Nanotechnology (CBEN) at Rice University had also looked at the results.

I'll cut to the chase on the tale of the rats.The study concludes, in part:

"Exposures to high-dose (5 mg/kg) SWCNT produced mortality in ~15% of the SWCNT-instilled rats within 24 h postinstillation. This mortality resulted from mechanical blockage of the upper airways by the instillate and was not due to inherent pulmonary toxicity of the instilled SWCNT particulate."

Kevin Ausman CBEN's executive director, supplied me with a wonderfully understandable translation during a conversation I had with him a month ago in Chicago:

What that means is that if you look at just the cross-sections of the lungs, "Uh-oh. Bad things are happening." If you look at the biochemistry of what's going, almost nothing seems to be going on. And so the normal biochemical tags for, "something bad is happening" aren't telling something bad is happening."

Here's my translation of the translation: The rats were definitely dead (and I believe they are still dead, although I have yet to confirm this). The nanotubes were definitely the guilty party. But the late rodents met their rat makers by suffocation, and not necessarily from any poison in the tiny tubes.

Plus, what the researchers did, as Ausman explained it to me, was basically disperse the nanotubes into a soap-and-water solution and inject it into the lungs, avoiding the whole issue of how the nanotubes ever got there in the first place.

This is how science works. Small steps, each study building on the conclusions of others. Nanotubes might, as the slogan goes these days, turn out to be the "next asbestos," but it is far too early to convict them of anything except being in the wrong rats at the wrong time.

For more on DuPont and nanotubes, here's an excellent report from The News Journal of Delaware. And more background can be found on Small Times here and here.