Carbon Nanotubes: A Summary of Beneficial and Dangerous Aspects of an Increasingly Popular Group of Nanomaterials

Our plain-English summary of Carbon Nanotubes: A Summary of Beneficial and Dangerous Aspects of an Increasingly Popular Group of Nanomaterials, by C. Zhang, L. Wu, M. de Perrot, et al (Frontiers in Oncology, 2021).

The study

• Authors: C. Zhang, L. Wu, M. de Perrot, X. Zhao
• Journal: Frontiers in Oncology
• Published: 2021;11:693814
• Type of article: Review
• Cited by: 35 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Carbon nanotubes (CNTs) are nanomaterials with broad applications that are produced on a large scale. Animal experiments have shown that exposure to CNTs, especially one type of multi-walled carbon nanotube, MWCNT-7, can lead to malignant transformation. CNTs have characteristics similar to asbestos (size, shape, and biopersistence) and use the same molecular mechanisms and signaling pathways as those involved in asbestos tumorigenesis. Here, a comprehensive review of the characteristics of carbon nanotubes is provided, as well as insights that may assist in the design and production of safer nanomaterials to limit the hazards of currently used CNTs.

Copyright © 2021 Zhang, Wu, de Perrot and Zhao.

In plain English

This article was a review, not a new study. The authors summarized published research on carbon nanotubes (CNTs), which they described as similar to asbestos in size, shape and biopersistence. They covered medical uses of CNTs, animal studies of how CNT features such as length, diameter and rigidity affect the pleura, cell and gene mechanisms, and regulation. They wrote that research on CNT-induced mesothelioma is limited to animal experiments. Among the studies described, one reported mesothelioma in 87.5% of p53 heterozygous mice 84 days after a multi-walled type, MWCNT-7, was injected into the abdominal cavity at a dose of 3 mg per mouse. Another found that inhaled MWCNT-7 induced mesothelioma in mice only when combined with the carcinogen methylcholanthrene, not alone. The review stated that rigid, needlelike CNTs were more likely to induce mesothelioma. It also stated that in 2014 the International Agency for Research on Cancer classed MWCNT-7 as 'possibly carcinogenic to humans'. The authors noted a lack of epidemiologic evidence linking CNTs to mesothelioma in humans. They concluded that multi-walled CNTs represent a potential new carcinogen able to cause malignant pleural mesothelioma, and called for exposed workers to be followed up.

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: Narrative review of published research (medical applications, animal experiments, cell and molecular studies, and regulation of carbon nanotubes)
• Who was studied: No human population was studied. The review covered published animal studies (mainly mice and rats) and laboratory studies of human mesothelial cells exposed to carbon nanotubes.
• Exposure: Carbon nanotubes, both single-walled (SWCNTs) and multi-walled (MWCNTs), especially the multi-walled type MWCNT-7. Routes in the reviewed animal studies included inhalation, intratracheal administration, intrapleural, intraperitoneal and intrascrotal injection.
• Main results:
  • The authors stated that research on CNT-induced mesothelioma is limited to animal experiments.
  • In one cited study, MWCNT-7 was injected into the abdominal cavity at a dose of 3 mg per mouse. Mesothelioma developed in 87.5% of p53 heterozygous mice after 84 days.
  • In one cited inhalation study, MWCNT-7 given together with the carcinogen methylcholanthrene induced mesothelioma, while mice given MWCNT-7 alone did not develop mesothelioma.
  • From the animal injection studies reviewed, the authors summarized that rigid, needlelike CNTs about 5 µm long and 50 nm in diameter are more likely to induce mesothelioma.
  • The review reported that in 2014 the International Agency for Research on Cancer classified MWCNT-7 as possibly carcinogenic to humans (Group 2B). Other types of CNTs were classed as not classifiable (Group 3).
  • The review reported that CNTs have been found in the lung tissue of patients exposed to World Trade Center dust and in airway fluid of asthmatic Parisian children.
• The authors' conclusion: The authors concluded that multi-walled CNTs represent a potential new carcinogen able to cause malignant pleural mesothelioma. They wrote that workers regularly exposed to CNTs should be followed up.
• Limitations the authors state:
  • The authors noted there is no epidemiologic evidence linking CNTs to malignant pleural mesothelioma in humans.
  • The authors noted that mesothelioma and lung damage from CNT exposure have not been systematically investigated.

Topics

Medical terms in this study, explained in our Lexicon: Malignant Transformation, biopersistence, Carcinogenesis.

Related studies

• Genotoxicity of carbon nanofibers: are they potentially more or less dangerous than carbon nanotubes or asbestos? — E.R. Kisin, A.R. Murray, et al. (2011)
• Carcinogenic Potential of High Aspect Ratio Carbon Nanomaterials — S. Luanpitpong, L. Wang, et al. (2016)
• Structural defects play a major role in the acute lung toxicity of multiwall carbon nanotubes: physicochemical aspects — I. Fenoglio, G. Greco, et al. (2008)
• Aspect ratio has no effect on genotoxicity of multi-wall carbon nanotubes — J.S. Kim, K. Lee, et al. (2011)
• Threshold Rigidity Values for the Asbestos-like Pathogenicity of High-Aspect-Ratio Carbon Nanotubes in a Mouse Pleural Inflammation Model — D.K. Lee, S. Jeon, et al. (2018)
• A review of exposure and toxicological aspects of carbon nanotubes, and as additives to fire retardants in polymers — A. Christou, A.A. Stec, et al. (2016)

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