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ENVIROETHICS  2006

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Subject:

Re: Nano Tech? The New GM?

From:

STEVEN BISSELL <[log in to unmask]>

Reply-To:

Discussion forum for environmental ethics.

Date:

Mon, 5 Jun 2006 08:01:30 -0600

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (92 lines)

I have never seen any evidence linking pollution
>to Nano-Tech at all. I think you are correct.
>I was just curious if anyone looked at the authors
>background.
>
>Lisa
>


It seems that Gunter Oderdoster is a well respected expert in the problems 
of enhalation of ultra small particles. 
http://www2.envmed.rochester.edu/envmed/TOX/faculty/oberdoerster.html 
However he has said, "I'm not advocating that we stop using nanotechnology, 
but I do believe we should continue to look for adverse health effects," as 
quoted in this article  
http://www.in-pharmatechnologist.com/news/ng.asp?id=51273 in a phamaceutical 
news letter.

This statement is kind of at odds with what was quoted in the Montague 
article; "The petition to FDA says, "Engineered nanoparticles have 
fundamentally different properties from their bulk material counterparts -- 
properties that also create unique human health and environmental risks -- 
which necessitate new health and safety testing paradigms." And this is 
confirmed by scientists like Gunter Oberdorster who has written text books 
on the subject and a recent review of 'nanotoxicology'.

This review is given here in full, but again the operative conclusion of 
Oderdoster was "Therefore, whether the generally recognized principles of 
fiber toxicology apply to these nanofiber structures needs still to be 
determined (Huczko et al. 2001)."

Montaque's article does not include these caveats but suggests that 
Oderdoster is concluding that nano-particles are toxic. Again this seems, to 
me, to be a lot like the 'debate' over GM foods, no evidence of harm, but a 
strong suspicion of science and technology and an over zealous application 
of the precautionary principle.

Here's the full review which I got off the web from LookSmart 
http://www.findarticles.com/

Engineered nanomaterials can have very different shapes, for example, 
spheres, fibers, tubes, rings, and planes. Toxicologic studies of spherical 
and fibrous particles have well established that natural (e.g., asbestos) 
and manmade (e.g., biopersistent vitreous) fibers are associated with 
increased risks of pulmonary fibrosis and cancer after prolonged exposures 
[Greim et al. 2001; International Agency for Research on Cancer (IARC) 
2002]. Critical parameters are the three Ds: dose, dimension, and durability 
of the fibers. Fibers are defined as elongated structures with a 
diameter-to-length ratio (aspect ratio) of 1:3 or greater and with a length 
of > 5 [micro]m and diameter [less than or equal to] 3 [micro]m [World 
Health Organization (WHO) 1985]. Carbon nanotubes have aspect ratios of up 
to [greater than or equal to] 100, and length can exceed 5 [micro]m with 
diameters ranging from 0.7 to 1.5 nm for single-walled nanotubes, and 2 to 
50 nm for multiwalled nanotubes. Results from three studies using 
intratracheal dosing of carbon nanotubes in rodents indicate significant 
acute inflammatory pulmonary effects that either subsided in rats (Warheit 
et al. 2004) or were more persistent in mice (Lam et al. 2004; Shvedova et 
al. 2004b). Administered doses were very high, ranging from 1 to 5 mg/kg in 
rats; in mice doses ranged from 3.3 to 16.6 mg/kg (Lam et al. 2004) or 
somewhat lower, from 0.3 to 1.3 mg/kg (Shvedova et al. 2004a). Granuloma 
formation as a normal foreign body response of the lung to high doses of a 
persistent particulate material was a consistent finding in these studies. 
Metal impurities (e.g., iron) from the nanotube generation process may also 
have contributed to the observed effects. Although these in vivo first 
studies revealed high acute effects, including mortality, this was explained 
by the large doses of the instilled highly aggregated nanotubes that caused 
death by obstructing the airways and should not be considered a nanotube 
effect per se (Warheit et al. 2004). In vitro studies with carbon nanotubes 
also reported significant effects. Dosing keratinocytes and bronchial 
epithelial cells in vitro with single-walled carbon nanotubes (SWNTs) 
resulted in oxidative stress, as evidenced by the formation of free 
radicals, accumulation of peroxidative products, and depletion of cell 
antioxidants (Shvedova et al. 2004a, 2004b). Multiwalled carbon nanotubes 
(MWNTs) showed proinflammatory effects and were internalized in 
keratinocytes (Monteiro-Riviere et al. 2005). Again, the relatively high 
doses applied in these studies need to be considered when discussing the 
relevancy of these findings for in vivo exposures. A most recent study in 
macrophages comparing SWNTs and MWNTs with [C.sub.60] fullerenes found a 
cytotoxicity ranking on a mass basis in the order SWNT > MWNT > [C.sub.60]. 
Profound cytotoxicity (mitochondrial function, cell morphology, phagocytic 
function) was seen for SWNTs, even at a low concentration of 0.38 
[micro]g/[cm.sup.2]. The possible contribution of metal impurities of the 
nanotubes still needs to be assessed. Therefore, whether the generally 
recognized principles of fiber toxicology apply to these nanofiber 
structures needs still to be determined (Huczko et al. 2001).

Steven

"In order to be old and wise one
must first be young and stupid."
               T-Shirt in New Zealand

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