Single- and multi-wall carbon nanotubes versus asbestos: are the carbon nanotubes a new health risk to humans?

Our plain-English summary of Single- and multi-wall carbon nanotubes versus asbestos: are the carbon nanotubes a new health risk to humans?, by M. Pacurari, V. Castranova, V. Vallyathan (Journal of Toxicology and Environmental Health. Part a, 2010).

The study

• Authors: M. Pacurari, V. Castranova, V. Vallyathan
• Journal: Journal of Toxicology and Environmental Health. Part a
• Published: 2010;73(5):378-95
• Type of article: Review
• Cited by: 90 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Carbon nanotubes (CNT), since their discovery, have become one of the most promising nanomaterials in many industrial and biomedical applications. Due to their unique physicochemical properties, interest is growing in the manufacture of CNT-based products and their subsequent marketing. Since their discovery, the prospect of possible undesirable human health effects has been a focus of many scientific studies. Although CNT possess unique physical properties that include (1) nanoscale diameter, (2) a wide length distribution ranging from tens of nanometers to several micrometers, and (3) high aspect ratio, the fibrous-like shape and durability suggest that their toxic properties may be analogous to those observed with other fibrous particles, such as asbestos. The present study provides a summary of published findings on CNT bioactivity, such as the potential of CNT, especially of multi-wall carbon nanotubes (MWCNT), to activate signaling pathways modulating transcription factor activity, induce apoptosis, induce DNA damage, and initiate biological responses. Assessment of risks to human health and adoption of appropriate exposure controls is critical for the safe and successful introduction of CNT -based products for future applications.

In plain English

This article was a review of published laboratory and animal studies on single-wall and multi-wall carbon nanotubes, compared mainly with crocidolite asbestos. It did not report new experiments. The reviewed cell studies, including the authors' earlier work on human mesothelial cells, found that both nanotube types caused DNA damage, cell death and cell-signaling activation. In the mesothelial cell studies, at similar mass doses, crocidolite was the most toxic and single-wall nanotubes the least. Among animal studies, a Japanese team reported mesothelioma in p53 heterozygous mice injected in the abdominal cavity with 3 mg per mouse of multi-wall nanotubes, a dose others criticized as extremely high. Another study reported asbestos-like inflammation of the abdominal wall in mice from long multi-wall nanotubes, but not from short ones. The authors suggested that the fiber-like shape and durability of nanotubes may make their toxic properties analogous to asbestos. They noted that few studies exist, that evidence of movement beyond the lung was preliminary and only for multi-wall nanotubes, and that long-term persistence in the lung remained unestablished.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review of published studies on carbon nanotube toxicity compared with asbestos
• Who was studied: Published cell-culture (in vitro) and animal (in vivo) studies, including human mesothelial cells and mice and rats; no human population studied
• Exposure: Single-wall (SWCNT) and multi-wall (MWCNT) carbon nanotubes, compared with crocidolite asbestos
• Main results:
  • In the reviewed mesothelial cell studies (Pacurari et al. 2008a, 2008b), at similar mass concentrations crocidolite was more potent than MWCNT.
  • When SWCNT, MWCNT and asbestos were compared at similar mass doses in mesothelial cells, asbestos was most toxic and SWCNT least.
  • Takagi et al. (2008) reported mesothelioma after 144 days in p53 heterozygous mice given a high dose of MWCNT by intraperitoneal injection. The relevance of this study was questioned because of the extremely high dose.
  • Poland et al. (2008) reported that long MWCNT (longer than 15 µm) placed in the abdomen of mice caused asbestos-like inflammation of the abdominal wall and granulomas, while short MWCNT did not.
  • Lam et al. (2004) reported dose-dependent lung granulomas in mice after intratracheal SWCNT. Warheit et al. (2004) reported in rats granulomas that did not progress beyond 1 month after exposure.
  • In a preliminary, unpublished study cited as a personal communication (Hubbs et al.), 50% of mice exposed to MWCNT by pharyngeal aspiration had MWCNT-laden macrophages in the pleural lymphatics.
• The authors' conclusion: The authors suggested that the fiber-like shape and durability of carbon nanotubes may make their toxic properties analogous to those of fibrous particles such as asbestos.
• Limitations the authors state:
  • Few experimental studies provide evidence of an asbestos-like response to nanotubes.
  • There are no major studies on whether nanotubes move from the lung to other sites. Evidence for MWCNT was preliminary, and such movement of SWCNT had not been demonstrated.
  • Whether nanotubes persist in the lung the way amphibole asbestos does needs studies with longer observation periods.

Topics

Medical terms in this study, explained in our Lexicon: Discovery, Aspect Ratio (Length-to-diameter ratio), Apoptosis.

Related studies

• Raw single-wall carbon nanotubes induce oxidative stress and activate MAPKs, AP-1, NF-kappaB, and Akt in normal and malignant human mesothelial cells — M. Pacurari, X.J. Yin, et al. (2008)
• Neoplastic-like transformation effect of single-walled and multi-walled carbon nanotubes compared to asbestos on human lung small airway epithelial cells — L. Wang, T.A. Stueckle, et al. (2014)
• Carboxylated short single-walled carbon nanotubes but not plain and multi-walled short carbon nanotubes show in vitro genotoxicity — M. Mrakovcic, C. Meindl, et al. (2015)
• Induction of mesothelioma in p53+/- mouse by intraperitoneal application of multi-wall carbon nanotube — A. Takagi, A. Hirose, et al. (2008)
• Dose-dependent mesothelioma induction by intraperitoneal administration of multi-wall carbon nanotubes in p53 heterozygous mice — A. Takagi, A. Hirose, et al. (2012)
• Distinct autophagy-apoptosis related pathways activated by Multi-walled (NM 400) and Single-walled carbon nanotubes (NIST-SRM2483) in human bronchial epithelial (16HBE14o-) cells — M. Ghosh, S. Murugadoss, et al. (2020)

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