Surface modification can affect the carcinogenicity of asbestos

Our plain-English summary of Surface modification can affect the carcinogenicity of asbestos, by R.C. Brown, P. Carthew, J.A. Hoskins, et al (Carcinogenesis, 1990).

The study

• Authors: R.C. Brown, P. Carthew, J.A. Hoskins, E. Sara, C.F. Simpson
• Journal: Carcinogenesis
• Published: 1990;11(10):1883-5
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A sample of amosite asbestos was modified by effectively adding C8 and C18 hydrocarbon chains to the fibre surfaces. The altered fibres interacted less readily with cells in vitro and were less cytotoxic. In whole animals the number of mesotheliomas produced by the C8 material was the same as that with the parent material but the tumours occurred earlier. The C18 derivatized fibre was markedly less active in the production of tumours. This is the first report demonstrating that similar size fibres with differing surfaces have different pathogenic properties.

In plain English

This short communication reported laboratory tests of whether chemically changing the surface of asbestos fibres changes their effects. The authors treated a standard sample of amosite asbestos (UICC Amosite) to attach short (C8) or long (C18) hydrocarbon chains to the fibre surfaces. A comparison sample went through the same process without the added chemical ('sham-derivatized'). In cell culture, both treated fibres were less toxic to V79-4 cells than the sham-derivatized fibre. Both also attached to cells less readily, with the smaller reduction for the C8 fibre. Male LACP rats received 20 mg of fibre into the pleural cavity and were allowed to live until they died or showed distress. In each of the sham-derivatized and C8 groups, 4 of 10 rats developed large mesotheliomas, and two of the C8 tumours developed early. With the C18 fibre, one rat developed a very small tumour on the diaphragm. The difference was significant at the 5% level with a simple two-sample proportion test, but not with Fisher's exact test. The authors noted the groups were small. They suggested that fibre surface is an important determinant of biological activity.

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: Short communication reporting laboratory experiments: cell culture (in vitro) tests of cell survival and fibre/cell attachment, plus an animal experiment the authors call a life-time study, with intrapleural injection in rats that were allowed to live until they died or showed distress
• Who was studied: V79-4 cells in culture, and male LACP rats in four groups (sham-derivatized amosite, C8-amosite, C18-amosite, and a saline/DMSO control). The text gives 10 rats for each of the sham-derivatized and C8 groups. It does not state the size of the C18 or control groups. The work was done at the MRC Toxicology Unit, Carshalton, UK; study dates are not given.
• Exposure: UICC Amosite asbestos in three forms: sham-derivatized (heated and boiled in dry toluene), C8-Amosite (treated with octyldimethylchlorosilane) and C18-Amosite (treated with octadecyldimethylchlorosilane). Each rat received 20 mg of fibre in 0.5 ml of vehicle, or vehicle alone, injected into the pleural cavity.
• Main results:
  • In V79-4 cell culture, both surface treatments (C8 and C18) reduced the toxicity of the amosite compared with sham-derivatized amosite.
  • Both surface treatments reduced fibre/cell attachment. The effect of the C8 treatment was smaller than that of the C18 treatment.
  • In each of the sham-derivatized amosite and C8 groups, 4/10 rats developed large compressing mesotheliomas. Two of the tumours in the C8 group developed early. The tumours were the probable causes of death.
  • The article's own abstract states that the number of mesotheliomas produced by the C8 material was the same as with the parent material, but the tumours occurred earlier.
  • In the C18 group, only one rat developed a tumour, which was very small and on the pleural diaphragm.
  • Differences between the groups were significant at the 5% level using a simple two-sample proportion test, but not using Fisher's exact test.
  • Treatment raised the carbon content of the fibre from undetectable levels in the sham-derivatized material to 0.58% in the C8 fibre and 0.60% in the C18 fibre.
• The authors' conclusion: The authors suggested that the nature of a fibre's surface is an important determinant of its biological activity. Because the C8 material was not less carcinogenic than the sham-derivatized amosite, they suggested that surface changes must be large to affect carcinogenicity. They also suggested that fibres of the sizes thought to be hazardous are not all equally active, and that it might be premature to regard all products containing such fibres as posing a risk to humans.
• Limitations the authors state:
  • The authors stated that the difference in tumour incidence is difficult to analyse because small groups of animals were used and more than one tumour can develop in each exposed animal.
  • The group differences were not statistically significant when Fisher's exact test was used.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Amosite, Mesothelioma.

Related studies

• Modification of the in vitro activities of amosite asbestos by surface derivatization — P.H. Evans, R.C. Brown, et al. (1983)
• A reappraisal of the carcinogenicity of surface modified asbestos fibres — P. Carthew, R.E. Edwards, et al. (1993)
• Asbestos surface provides a niche for oxidative modification — H. Nagai, T. Ishihara, et al. (2011)
• Inorganic materials and living organisms: surface modifications and fungal responses to various asbestos forms — S. Daghino, E. Martino, et al. (2005)
• Synthetic chrysotile nanocrystals as a reference standard to investigate surface-induced serum albumin structural modifications — P. Sabatino, L. Casella, et al. (2007)
• Modification of biological surface activity of particles — R.J. Schnitzer (1974)

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