Fluoro-edenite and carbon nanotubes: The health impact of 'asbestos-like' fibres

Our plain-English summary of Fluoro-edenite and carbon nanotubes: The health impact of 'asbestos-like' fibres, by E. Miozzi, V. Rapisarda, A. Marconi, et al (Experimental and Therapeutic Medicine, 2016).

The study

• Authors: E. Miozzi, V. Rapisarda, A. Marconi, C. Costa, I. Polito, D.A. Spandidos, M. Libra, C. Fenga
• Journal: Experimental and Therapeutic Medicine
• Published: 2016;11(1):21-27
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Several decades have passed since Wagner et al demonstrated a causal link between asbestos fibre inhalation and the development of pleural mesothelioma in 1960. It was later suggested that pleural plaques are a benign consequence of exposure to these fibres. Most recently, a significant association between exposure to asbestos and cancer diagnosed at various sites, such as the peritoneum, stomach, pharynx, colon and ovaries has been demonstrated. The great concerns about public health that arose from the scientific evidence presented above have led to the banning of asbestos in several countries. Over the years, the suspicion that particles with a high aspect ratio may have asbestos-like pathogenicity has been supported by increasing evidence. Natural occurring minerals, as well as man-made fibres, have proven capable of inducing either chronic inflammation of serous membranes, or, in some cases, the development of peritoneal and pleural mesothelioma. The pathogenic role of both fluoro-edenite and carbon nanotubes, two 'asbestos-like' fibres is summarized and discussed in this review. The data presented herein support the notion that occupational exposure to these two types of fibre contributes to the development of different types of cancer.

In plain English

This article was a review, not a new study. The authors searched PubMed up to September 2015 for original laboratory and animal studies on two 'asbestos-like' fibres. One was fluoro-edenite, a volcanic mineral identified near Biancavilla, Sicily. The other was man-made carbon nanotubes. For fluoro-edenite, they described pleural mesothelioma in Biancavilla affecting males and females equally, a rat study reporting more mesotheliomas after injection into the abdomen, and cell studies in which fluoro-edenite, like crocidolite, caused DNA damage. For carbon nanotubes, the rodent studies they reviewed gave mixed results. Mice with a genetic susceptibility had a high incidence of peritoneal tumours after injection of multi-walled nanotubes. A two-year rat study found an above-average mesothelioma rate only in the crocidolite group (36%). Other studies linked fibre length to inflammation. The authors noted that IARC classed fibrous fluoro-edenite as carcinogenic to humans and one nanotube type as possibly carcinogenic. They concluded the data support a role for occupational exposure to both fibres in cancer. They also stated there are no real human data on nanotube carcinogenicity, and they called for further studies.

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 original in vivo and in vitro studies, based on a PubMed search up to September 2015
• Who was studied: Original animal (in vivo) and cell (in vitro) studies; the review's table lists 3 fluoro-edenite cell studies (2004 to 2011) and 5 carbon nanotube animal studies (2008 to 2015). It also discusses the population of Biancavilla, Sicily, Italy
• Exposure: Fluoro-edenite (a fibrous amphibole of volcanic origin from Monte Calvario, Biancavilla) and carbon nanotubes (single-walled and multi-walled). Crocidolite, amosite and tremolite asbestos appear as comparison fibres in the reviewed studies
• Main results:
  • In Biancavilla, pleural mesothelioma equally affected males and females, without correlation to asbestos exposure, and also affected young adults. The authors described this as a pattern more likely related to environmental exposure
  • A study by Soffritti et al reported a marked increase in mesotheliomas in rats injected with fluoro-edenite fibres into the peritoneal cavity
  • In a 2004 cell study by Cardile et al, both fluoro-edenite and crocidolite (5, 50 or 100 µg/ml) induced DNA damage and other cell effects; crocidolite showed greater toxicity
  • IARC classified fluoro-edenite fibrous amphibole as carcinogenic to humans (group 1)
  • IARC assessed MWCNT-7 as a possible carcinogen to humans (group 2B); other multi-walled and single-walled nanotubes were not classifiable
  • In a 2008 study by Poland et al, long carbon nanotubes injected into the mouse peritoneal cavity were retained at the mesothelial surface, with marked inflammation and granulomas. Short nanotubes, carbon black and amosite were used as controls
  • In a 2008 study by Takagi et al, p53+/- mice (19 per group, 3 mg/animal by intraperitoneal injection) given multi-walled nanotubes were the first to reach 100% mortality, with a high incidence of macroscopic peritoneal tumours. The crocidolite group showed similar effects to a lesser extent. The fullerene group showed no pathological signs apart from black plaques
  • In a 2009 two-year study by Muller et al in rats, neither multi-walled nanotube type caused significant mesothelioma development; only the group injected with 2 mg crocidolite had an above-average incidence (36%)
  • In a 2012 mouse pleural injection study by Schinwald et al, there was a length-dependent inflammatory response to silver nanowires longer than 5 µm and to long amosite fibres; shorter fibres did not cause significant inflammation
  • In a 2015 study by Albini et al, mice were exposed to multi-walled nanotubes mixed into their litter. They showed no overt pathological sign, but nanotubes spread rapidly to tissues including the lungs, liver and brain, with macrophage accumulation and amyloid deposits
• The authors' conclusion: The authors concluded that the data support the notion that occupational exposure to fluoro-edenite and carbon nanotubes contributes to the development of different types of cancer. They also stated that further studies are needed to assess human risk at real doses and exposure times
• Limitations the authors state:
  • Human epidemiological studies were lacking in some cases, so animal studies were given precedence over cell studies
  • Real-life exposure is very unlikely to deliver doses of long multi-walled nanotubes like those injected in the animal studies
  • There are no real human data on the carcinogenicity of carbon nanotubes
  • The real level of fluoro-edenite exposure for Biancavilla inhabitants cannot be assessed

Topics

Medical terms in this study, explained in our Lexicon: fluoro-edenite, Pleural Mesothelioma, Pleural Plaques, Peritoneum, Aspect Ratio (Length-to-diameter ratio), Chronic Inflammation, Occupational Exposure.

Related studies

• Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes — Y. Grosse, D. Loomis, et al. (2014)
• Fluoro-edenite induces fibulin-3 overexpression in non-malignant human mesothelial cells — V. Rapisarda, R. Salemi, et al. (2016)
• Detection of pleural plaques in workers exposed to inhalation of natural fluoro-edenite fibres — V. Rapisarda, C. Ledda, et al. (2015)
• Mineral fibre toxicity: expression of retinoblastoma (Rb) and phospho-retinoblastoma (pRb) protein in alveolar epithelial and mesothelial cell lines exposed to fluoro-edenite fibres — G. Musumeci, V. Cardile, et al. (2011)
• Monitoring of fluoro-edenite fibre pollution through the study of sheep lymph nodes as a model of a biological indicator — V. Rapisarda, G. Rapisarda, et al. (2005)
• Durability and inflammogenic impact of carbon nanotubes compared with asbestos fibres — M.J. Osmond-McLeod, C.A. Poland, et al. (2011)

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