Do Carbon Nanotubes and Asbestos Fibers Exhibit Common Toxicity Mechanisms?

Our plain-English summary of Do Carbon Nanotubes and Asbestos Fibers Exhibit Common Toxicity Mechanisms?, by S.S. Gupta, K.P. Singh, S. Gupta, et al (Nanomaterials, 2022).

The study

• Authors: S.S. Gupta, K.P. Singh, S. Gupta, M. Dusinska, Q. Rahman
• Journal: Nanomaterials
• Published: 2022;12(10)
• Type of article: Review
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

During the last two decades several nanoscale materials were engineered for industrial and medical applications. Among them carbon nanotubes (CNTs) are the most exploited nanomaterials with global production of around 1000 tons/year. Besides several commercial benefits of CNTs, the fiber-like structures and their bio-persistency in lung tissues raise serious concerns about the possible adverse human health effects resembling those of asbestos fibers. In this review, we present a comparative analysis between CNTs and asbestos fibers using the following four parameters: (1) fibrous needle-like shape, (2) bio-persistent nature, (3) high surface to volume ratio and (4) capacity to adsorb toxicants/pollutants on the surface. We also compare mechanisms underlying the toxicity caused by certain diameters and lengths of CNTs and asbestos fibers using downstream pathways associated with altered gene expression data from both asbestos and CNT exposure. Our results suggest that indeed certain types of CNTs are emulating asbestos fiber as far as associated toxicity is concerned.

In plain English

This article was a review, not a new experiment. The authors compared carbon nanotubes (CNTs) with asbestos fibers. CNTs are engineered carbon fibers made in single-wall and multi-wall forms. The authors drew on previously published studies, mostly in cells and animals, including studies of crocidolite and chrysotile asbestos. They organized the evidence around four proposed ways asbestos causes disease: oxidative stress, chromosome damage, adsorption of toxic substances onto fiber surfaces, and chronic inflammation. For each one, the authors wrote that the studies they reviewed suggested CNTs and asbestos act in similar ways. They also described gene-expression studies. In one cited study of human bronchial cells, 12 mesothelioma-related and 22 lung cancer-related genes changed more than two-fold after exposure to both asbestos and multi-wall CNTs. The authors noted three caveats: CNT types differ substantially, not all high-aspect-ratio nanomaterials are linked to mesothelioma, and gene-expression results have been controversial. The authors concluded that asbestos and CNTs of certain diameters and lengths share common disease mechanisms. They called for a protocol to regulate the industrial use of some CNTs.

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 studies comparing carbon nanotubes and asbestos fibers; no new data were collected
• Who was studied: No study population of its own; the review covered previously published studies, mostly in cultured cells and in rats and mice
• Exposure: Single-wall and multi-wall carbon nanotubes (SWCNT, MWCNT), compared with asbestos fibers; the cited asbestos studies mainly used crocidolite and chrysotile
• Main results:
  • The review was organized around four proposed mechanisms of asbestos-induced disease
  • Oxidative stress: the authors wrote that the reviewed studies indicated a shared mechanism for asbestos and CNTs
  • Genetic damage: the authors wrote that the reviewed studies suggested both asbestos and CNTs damage chromosomes and DNA
  • Adsorption: the authors described the fate of carcinogenic compounds adsorbed on CNTs as a concern, as for asbestos
  • Chronic inflammation: the authors wrote that asbestos and certain carbon nanofibers share inflammation mechanisms, mainly attributed to fibrous structure
  • In a cited study by Kim and co-workers on normal human bronchial epithelial cells exposed to crocidolite or MWCNTs, 12 mesothelioma-related and 22 lung cancer-related genes changed more than two-fold with both exposures
• The authors' conclusion: The authors concluded that asbestos and CNTs of certain diameters and lengths share common mechanisms of disease. They called for a protocol to regulate the industrial use of some CNTs.
• Limitations the authors state:
  • The authors noted that gene-expression (toxicogenomics) studies of asbestos and CNTs gave controversial results because of differences in fiber length, diameter, surface area, purity and dispersion
  • The authors noted that CNT types differ substantially and cannot be judged on chemical composition alone
  • The authors noted that not all high-aspect-ratio nanomaterials are associated with mesothelioma, and that fiber shape is not the only factor

Related studies

• A critical review of the biological mechanisms underlying the in vivo and in vitro toxicity of carbon nanotubes: The contribution of physico-chemical characteristics — H.J. Johnston, G.R. Hutchison, et al. (2010)
• Mechanisms of pulmonary toxicity and medical applications of carbon nanotubes: Two faces of Janus? — A.A. Shvedova, E.R. Kisin, et al. (2009)
• Differences and similarities between carbon nanotubes and asbestos fibers during mesothelial carcinogenesis: shedding light on fiber entry mechanism — H. Nagai, S. Toyokuni (2012)
• Thirteen-week study of toxicity of fiber-like multi-walled carbon nanotubes with whole-body inhalation exposure in rats — T. Kasai, Y. Umeda, et al. (2015)
• Long, needle-like carbon nanotubes and asbestos activate the NLRP3 inflammasome through a similar mechanism — J. Palomäki, E. Välimäki, et al. (2011)
• The mechanism of pleural inflammation by long carbon nanotubes: interaction of long fibres with macrophages stimulates them to amplify pro-inflammatory responses in mesothelial cells — F.A. Murphy, A. Schinwald, et al. (2012)

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