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
