I nanomodifisert epoksy fra Bayer er nanorørene lagt inn i materialet hos produsenten og nanorørene frigjøres ikke under viderebearbeiding av materialene, blir det opplyst fra produsenten av "Baytube". Det dreier seg også om korte og myke nanorør som det ikke er vist kan være helsefarlige. Produktet fra Bayer er forøvrig ikke testet i forbindelse med det arbeidet Nature Nanotechnology viser til.
I sine kommentarer understreker Bayer at det er anerkjent på forskerhold at strukturen til nanorørene er avgjørende for om de er helseskadelige. Det kan derfor ikke sies noe generelt om helsevirkningen av nanorør. Forskning pågår for å finne ut mer om virkningene.
SFT har tidligere opplyst at det er et stort behov for mer forskning på mulige helse- og miljøeffekter av nanopartikler. Det bidrar til utvikling av regelverk og metoder for risikovurdering for nanomaterialer i EU og OECD.
SFT understreker at det foreløpig spesielt er én gruppe nanomaterialer - frie produserte nanopartikler - som har kommet i søkelyset. Det er påvist at enkelte typer av disse partiklene kan ha negative helse- og miljøeffekter.
Nanopartikler som er bundet til en overflate, eller materialer hvor nanostrukturen er en del av et større objekt, gir imidlertid mindre grunnlag for bekymring.
Les kommentarene fra Bayer her:
Poland et al. study on potential asbestos-like effects of CNTs
Published May 20, 2008 in "Nature Nanotechnology"
On May 20, 2008, Poland et al. published a study in the peer reviewed magazine "Nature
Nanotechnology". They report that some relatively rigid and long Carbon Nanotubes (CNTs)
can cause effects in mice that are similar to the effects known from asbestos or other long
rigid inhalable fibres (for details please see page 3 of this document). In contrast, other CNTs with a different morphology ("short and tangled") displayed no pathogenic fibre effects. The focus of this mechanistic study is on finding evidence of inherent hazard of CNTs (i.e. the pure potential to produce a harmful effect), whereas dose-response-relationship and longterm consequences were not examined. The actual risk of an inherent hazard to become
reality (i.e. whether exposure could happen to a sufficient extent that an adverse effect might occur) is not investigated.
Further research is needed – at present no relevance for human health
This is a preliminary mechanistic study. Nevertheless, on a general perspective, the results
seem to add to the growing amount of evidence that there is indeed a relationship between
the structure of CNTs and their potential pathogenic activity. However, as this is a preliminary
examination, the study findings require further research to better understand the
structure/activity relationship of CNTs.
Most importantly, the study shows very clearly that a "generalisation" for all CNTs is not
possible. There are many different kinds of CNTs; they behave differently and therefore they
must be assessed case by case. From the results of this study, no conclusions can be drawn
with respect to potential health effects for humans. A risk to humans must be assessed as a
result of the potential of a substance to cause adverse effects including assessment of doseresponse relationship and the realistic exposure level of humans to the substance. The study did not investigate these points.
Baytubes® are safe for use
For users of Baytubes® in the industrial value chain, as well as for end-consumers, there is
no realistic potential for inhalative exposure to Baytubes®. Main applications of Baytubes®
are improving polymers and coatings. In these applications, the particles are firmly
embedded in the polymer structure of the final product. In addition, Baytubes® material
comes as large agglomerates of CNTs, not as single fibres; more than 99% of the material is not inhalable thus providing an additional safety factor.
Baytubes® and asbestos are essentially different
Asbestos fibres and Baytubes® are essentially different in terms of their composition and
mechanical properties: In contrast to the long and rigid CNT fibres in the study with some
resemblance to asbestos fibres and where the effects were seen, Baytubes® are short
spiral-shaped, entangled and flexible, forming a kind of cotton ball. As such, they appear to
have similiarities with the short/tangled samples in the Poland et al. study, which did not
show any pathogenic fiber’s effects. All existing standard "Good Laboratory Practices" (GLP)
guideline studies performed so far with Baytubes® gave no evidence of relevant adverse
effect at realistic exposure levels (including oral, dermal and inhalative acute studies).
Bayer MaterialScience (BMS) Product Stewardship Program for CNTs
At present, the potential adverse effects following inhalation exposure to CNTs are not
sufficiently understood. To close the knowledge gap in the area of inhalative exposure to
CNTs, BMS initiated a sub-chronic inhalation guideline study. In line with the principles of
Responsible Care, Bayer MaterialScience ensures that production of CNTs takes place in
closed, automated reactors and closed containments, with personal protection equipment
applied; the technical measures for safety integrated into the plant design ensure that no
unreasonable exposure to employees or the environment occurs. For the time being and as
long as the chronic potential effects have not been fully investigated, Bayer MaterialScience
doesn’t recommend the use of Baytubes® in applications for end-consumers where a
potential for inhalative exposure exists (e.g. spray).
Furthermore, as one of the founding partners in PACTE (Producers’ Association of Carbon
Nanotubes in Europe, a sector group of Cefic, the European Chemical Industry Association),
BMS cooperates with other major CNT producers in Europe to help members companies
fulfill their responsibilities as set in the principles of Responsible Care. This has resulted for
example in the development of a common Code of Good Conduct that is available on the
internet (www.cefic.org, search for PACTE). Bayer MaterialScience also actively contributes
to nanomaterial safety research projects funded by the German Ministry of Education and
Research (BMBF), such as NanoCare and TRACER. One focus in these initiatives is the
development of further measuring methods to monitor potential exposure at the workplace or of further toxicological testing procedures in vitro and in vivo.
Contact: Dr. Jacques Ragot
Bayer MaterialScience AG
E1 North 51368 Leverkusen, Germany
"Carbon nanotubes introduced into the abdominal cavity display asbestos-like
pathogenic behaviour in a pilot study"
Craig A Poland, Rodger Duffin, Ian Kinloch; Andrew Maynard, William AH
Wallace, Anthony Seaton, Vicki Stone, Simon Brown, William MacNee
and Ken Donaldson
What was the intention of the study?
Based on the hypothesis that the needle-shaped form of some CNT fibres is comparable to that of asbestos, the authors searched for acute pathogenic effects from CNT fibres in the mesothelial lining of the body cavity of mice. The goal was to examine whether CNTs show comparable adverse effects as known from asbestos (so-called "fibre pathogenic paradigm", assuming that fibres thinner than 3 micrometer and longer than 20 micrometer, and persistent in the lung, are harmful).
What did the authors do?
The study investigated 4 samples of two kinds of CNTs: long, rather straight and rigid ones, and short, tangled flexible ones. A single high dose of CNT (50 microgram) was injected into the abdomen of the mice, to see whether adverse effects such as inflammation or lesions of the body cavity lining tissue (mesothelium) would appear shortly after exposure (measured at day 1 and 7 after application).The authors did not investigate whether such effects would actually lead to longterm adverse effects, e.g. to develop cancer in the mice. Also, the authors did not examine whether an exposure through inhalation could reach a (yet undefined) threshold showing an adverse effect, nor whether the amount of CNT that might eventually reach the tissue through inhalation (the most realistic exposure route) would be sufficient to produce an effect.
What are the results of the study?
The data demonstrate that acute asbestos-like pathogenic behaviour associated with CNT seem to conform to a structure/activity relationship based on length. This appears to be consistent to the behaviour of asbestos and other fibres. However, the authors show clear differences between long and short/tangled samples of CNTs: While their statistical analysis shows no significant effect from the short tangled CNT samples, i.e. they did not mimic the behaviour of long asbestos fibres, the long rigid samples indicated an effect that is similar to the one known from asbestos (inflammation and lesions) in the acute study.
How can the results be explained?
Depending on the size and shape of fibres the body reacts differently. This is mainly due to
the ability of the cells to handle the respective fibres. One interpretation for the findings in the Poland et al. preliminary study could be, that the long and rigid CNTs are too long for the cells to manage, thus "frustrating" them and producing adverse effects – resulting in pathogenic effects comparable to those seen with asbestos, whereas the short CNTs which are entangled, thus forming a flexible, soft "ball", are not displaying pathogenic fiber effect. Further research is needed to understand the exact toxicological mechanisms underlying the effects and to further define the structure/activity relationship.