Carcinogenic Potential of High Aspect Ratio Carbon Nanomaterials

Our plain-English summary of Carcinogenic Potential of High Aspect Ratio Carbon Nanomaterials, by S. Luanpitpong, L. Wang, D.C. Davidson, et al (Environmental Science. Nano, 2016).

The study

• Authors: S. Luanpitpong, L. Wang, D.C. Davidson, H. Riedel, Y. Rojanasakul
• Journal: Environmental Science. Nano
• Published: 2016;3(3):483-493
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Engineered nanomaterials, including high aspect ratio carbon nanomaterials, are often commercialized without a complete human risk assessment and safety evaluation. A health concern has been raised that high aspect ratio nanomaterials such as carbon nanotubes may cause unintended health consequences, such as asbestos-like lung cancer and mesothelioma, when chronically inhaled. Considering the widespread industrial and clinical applications and the increasing incidence of human exposure to nanomaterials, it is important to address the issue of nanomaterial carcinogenicity in a timely manner. This review summarizes recent advances in nanomaterial genotoxicity and carcinogenicity with a focus on high aspect ratio carbon nanotubes, and discusses current knowledge gaps and future research directions.

In plain English

This article was a review, not a new study. The authors summarized published laboratory research on whether carbon nanotubes, very thin fiber-like engineered materials, can damage genetic material and cause cancer. Some of the reviewed studies compared nanotubes with asbestos. The authors noted that no reports of direct harm to humans from carbon nanotubes were available. In one reviewed mouse study, animals given a cancer-starting chemical plus inhaled multi-walled nanotubes (Mitsui #7) had lung tumors in 62%, compared with 13%, 22% and 14% for air, the chemical alone or nanotubes alone. In that combined group, 9% had tumors consistent with sarcomatous mesothelioma. In a two-year rat study, needle-like nanotubes injected into the abdomen induced mesothelioma, with more than 80% morbidity within a year. Another study of short nanotubes found no apparent mesothelioma. Cell studies found that nanotubes and asbestos both increased mesothelial cell growth and invasion, with the enzyme MMP-2 a key player in both; gene analyses suggested distinct signaling pathways for each. The authors concluded that evidence supports the carcinogenicity of certain types of nanotubes, though more long-term animal and human studies are needed.

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 in vivo (animal) and in vitro (cell) studies; no new data were reported
• Who was studied: Published studies in mice, rats and human cell lines (lung epithelial cells and mesothelial cells); no human study populations
• Exposure: Single-walled and multi-walled carbon nanotubes (including multi-walled nanotube Mitsui #7), given by instillation, aspiration, inhalation or injection into the abdominal cavity, or applied to cells; some studies compared them with asbestos
• Main results:
  • The authors stated that no reports on direct adverse health effects of carbon nanotubes in humans were available
  • In a reviewed mouse study, mice given the chemical MCA plus inhaled MWCNT (Mitsui #7) had an incidence of bronchoalveolar adenomas and adenocarcinomas of 62% at 17 months, versus 13% (air), 22% (MCA alone) and 14% (MWCNT alone)
  • In the same reviewed study, 9% of mice exposed to MCA and MWCNT had serosal tumors morphologically consistent with sarcomatous mesothelioma. The review stated that these findings indicate MWCNT Mitsui #7 acts as a lung tumor promoter but not a tumor initiator in mice
  • In a reviewed two-year study in Wistar rats (50 per group) given intraperitoneal injections, needle-like MWCNTs (diameter about 60 to 85 nm) induced mesothelioma with more than 80% morbidity within a year. Thinner, more curved nanotubes had slower tumor onset
  • Negative findings were also reported. In one reviewed study, short MWCNTs (less than 1 micrometre) injected into the abdominal cavity of rats produced no apparent mesothelioma over two years
  • In reviewed studies of human mesothelial cells chronically exposed to low-dose SWCNTs, MWCNTs or asbestos, increased cell proliferation and invasion were seen with all three
  • In those reviewed studies, functional and gene knockdown experiments identified MMP-2, a matrix-degrading enzyme, as a key player in the invasiveness of both nanotube- and asbestos-treated cells. Gene analyses suggested that, despite some common gene signatures, the two materials have distinct gene signaling pathways
  • The review reported that the International Agency for Research on Cancer (IARC) classified MWCNT Mitsui #7 as group 2B (possibly carcinogenic to humans). IARC considered other carbon nanotubes group 3 (not classifiable)
• The authors' conclusion: The authors concluded that accumulating evidence supports the carcinogenicity of certain types of carbon nanotubes, but that more long-term animal and human studies are needed
• Limitations the authors state:
  • The authors noted that rodents differ from humans in how they inhale nanotubes, which makes the doses reaching their lower airways highly variable
  • The authors stated that there are no specific guidelines or consistent frameworks for assessing the carcinogenicity of nanomaterials

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Aspect Ratio (Length-to-diameter ratio), Lung Cancer, Mesothelioma, Genotoxicity.

Related studies

• Effect of chemical composition and state of the surface on the toxic response to high aspect ratio nanomaterials — B. Fubini, I. Fenoglio, et al. (2011)
• An integrated approach to testing and assessment of high aspect ratio nanomaterials and its application for grouping based on a common mesothelioma hazard — F. Murphy, S. Dekkers, et al. (2021)
• A 3-dimensional in vitro model of epithelioid granulomas induced by high aspect ratio nanomaterials — V.C. Sanchez, P. Weston, 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)
• Carbon Nanotubes: A Summary of Beneficial and Dangerous Aspects of an Increasingly Popular Group of Nanomaterials — C. Zhang, L. Wu, et al. (2021)
• The carcinogenic potential of nanomaterials, their release from products and options for regulating them — H. Becker, F. Herzberg, et al. (2011)

Browse return to medical research.