Sunday, August 28, 2005

Nanotoxicology backs Macrohype of Nanoparticles

BrooklynDodger was attracted to this abstract because of wonder whether nanotoxicology is macrohype. The Dodger has already renamed fine particle health effects nanoparticle research.  Brooklyndodger skimmed the abstract and questioned, how do these indeces of toxicity compare to known particle toxicants?  The full text of the paper actually answers these questions; none of this very important data made the abstract.  [Reviewers’ and editors’ benign neglect?]

In parallel experiments, rats got 2 mg/rat of ultrafine carbon black and chrysotile asbestos, compared to the 0.5-2 mg/rat of ground and unground nanotubes. The investigators noted that “CB had a specific surface area of 66.8 m2/g,” an interesting number for which the Dodger has no comparison. The Dodger’s blog-quality review of the paper couldn’t find particle counts comparing nanotubes to the controls.  Particle counts may be more important than mass in comparing potency.  The actual particle size on inhalation of nanomaterials will be important.

Eyeballing the charts, all treatments were in the same ball park.  Asbestos at 2 mg was maybe more potent than nanotubes at 2 mg, which were somewhat more potent than ultrafine CB.  But CB was active.

So, nanotubes are maybe less potent than asbestos; not being as dangerous as the worst material in the world is hardly a safe use endorsement.  Carbon black is reliably carcinogenic in the rat and inadequately studied in the mouse;  these findings equate to “possibly carcinogenic” at IARC, and not classifiable at NTP [which demands two species.]  Taking mechanism into account, the Dodger would call nanotubes and CB carcinogenic.

The investigators invoke the “precautionary principle.”  The Dodger opines these data imply carcinogen designation without invoking the PP.  

Toxicology and Applied Pharmacology 207 (2005) 221– 231
Respiratory toxicity of multi-wall carbon nanotubes
Julie Mullera, Franc¸ois Huauxa, Nicolas Moreaub, Pierre Missona, Jean-Franc¸ois Heiliera,
Monique Delosc, Mohammed Arrasa, Antonio Fonsecab, Janos B. Nagyb, Dominique Lisona,T
aIndustrial Toxicology and Occupational Medicine Unit, Universite´ Catholique de Louvain, Clos Chapelle-aux-Champs, 30.54; 1200 Brussels, Belgium
bLaboratory of Nuclear Magnetic Resonance, Faculte´s Universitaires Notre-Dame de la Paix, Namur, Belgium
cLaboratory of Pathology, University Hospital of Mont-Godinne, Yvoir, Belgium
Received 14 September 2004; accepted 5 January 2005
Available online 5 March 2005

Carbon nanotubes focus the attention of many scientists because of their huge potential of industrial applications, but there is a paucity of information on the toxicological properties of this material. The aim of this experimental study was to characterize the biological reactivity of purified multi-wall carbon nanotubes in the rat lung and in vitro. Multi-wall carbon nanotubes (CNT) or ground CNT were administered intratracheally (0.5, 2 or 5 mg) to Sprague–Dawley rats and we estimated lung persistence, inflammation and fibrosis biochemically and histologically. CNT and ground CNT were still present in the lung after 60 days (80% and 40% of the lowest dose) and both induced inflammatory and fibrotic reactions. At 2 months, pulmonary lesions induced by CNT were characterized by the formation of collagen-rich granulomas protruding in the bronchial lumen, in association with alveolitis in the surrounding tissues. These lesions were caused by the accumulation of large CNT agglomerates in the airways. Ground CNT were better dispersed in the lung parenchyma and also induced inflammatory and fibrotic responses. Both CNT and ground CNT stimulated the production of TNF-a in the lung of treated animals. In vitro, ground CNT induced the overproduction of TNF-a by macrophages. These results suggest that carbon nanotubes are potentially toxic to humans and that strict industrial hygiene measures should to be taken to limit exposure during their manipulation.

D 2005 Elsevier Inc. All rights reserved. Keywords: Carbon nanotubes; Lung toxicity; Inflammation; Fibrosis  

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