Biological effects of tremolite

Our plain-English summary of Biological effects of tremolite, by J.C. Wagner, M. Chamberlain, R.C. Brown, et al (British Journal of Cancer, 1982).

The study

• Authors: J.C. Wagner, M. Chamberlain, R.C. Brown, G. Berry, F.D. Pooley, R. Davies, D.M. Griffiths
• Journal: British Journal of Cancer
• Published: 1982;45(3):352-60
• Cited by: 61 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Tremolite is an amphibole which has been implicated in a variety of disease patterns in different parts of the world. It occurs in a number of phases, which are chemically identical but have specific physical characteristics. In an attempt to clarify the epidemiological findings, tremolite fibres of 3 specific forms--A, B and C--were characterized and studied for biological activity by: (i) in vivo intrapleural injection of rats (2 separate experiments--1 with poor survival). (ii) in vitro enzyme release from mouse peritoneal macrophages (iii) in vitro giant-cell formation in A549 cultures (iv) in vitro cytotoxicity for V79-4 cells. Sample C, which contained more long thin fibres than A and B, was alone in producing mesotheliomas. C, but not A or B, induced LDH and B-glucuronidase enzyme release, and induced giant cells. A was not cytotoxic, B moderately cytotoxic and C as highly cytotoxic as UICC crocidolite. The in vivo studies were marred by being split between 2 experiments, of which the second had poor survival. We are aware of the weakness of our in vivo data, but as Tremolite C was being considered for commercial use on the European market we felt it timely to submit our findings for publication.

In plain English

The study tested three tremolite samples: flake-like Californian talc tremolite (A), medium-sized fibrous tremolite from Greenland (B) and fine-fibred tremolite from South Korea (C). Sample C contained many very long thin fibres, while A and B contained relatively few fibres. Sample A was injected into the pleural (chest) cavity of Wistar rats in one experiment. B and C were injected into Sprague-Dawley rats in a second, later experiment. Only Sample C produced mesotheliomas: 14 of 47 rats (30%), against none of 31 rats given Sample A and none of 48 given Sample B. In cell tests, only Sample C caused marked enzyme release from mouse macrophages and giant-cell formation in human tumour-derived lung cells. It was as toxic to hamster lung cells as UICC crocidolite. The authors noted that the second experiment had poor survival due to infection, and in it only 2 rats (6%) given crocidolite developed mesothelioma. The authors judged it wiser to read the data qualitatively. They concluded that they suspect Sample C would be a human health hazard if present in sufficient airborne concentration.

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: Animal experiment (injection of dust into the pleural cavity of rats, in two separate experiments) combined with laboratory cell-culture (in vitro) toxicity tests
• Who was studied: Experiment I used Wistar rats: 32 were given Sample A (31 examined), plus saline and SFA chrysotile control groups of 32. Experiment II used Sprague-Dawley rats: 48 each were injected with Samples B and C (48 and 47 examined), plus 32 given UICC crocidolite as a positive control and a saline control group (23 examined). Cell tests used mouse peritoneal macrophages, human tumour-derived A549 lung cells and Chinese hamster lung cells (V79-4). The work was done at the MRC Pneumoconiosis Unit, Penarth, Wales. Study dates are not stated.
• Exposure: Three tremolite samples were tested: A from Californian tremolitic talc (flake-like), B from Greenland (medium-sized fibrous) and C from South Korea (fine-fibred). In the animal experiments, each was given as a single 20 mg dose injected into the right pleural cavity. Sample A was tested in Wistar rats two years before Samples B and C were tested in Sprague-Dawley rats. In the cell tests, dusts were used at concentrations such as 50 to 200 micrograms per ml. UICC crocidolite and SFA chrysotile served as positive controls.
• Main results:
  • Mesotheliomas developed in 14 of 47 rats (30%) given tremolite Sample C. No rats given Sample A (31 examined) or Sample B (48 examined) developed mesothelioma.
  • In Experiment II, only 2 of 31 Sprague-Dawley rats (6%) given the UICC crocidolite positive control developed mesotheliomas.
  • Sample C contained 5.6 x 10^4 fibres longer than 8 micrometres and thinner than 1.5 micrometres per microgram, and UICC crocidolite contained 6.4 x 10^4 such fibres per microgram. Sample B contained none of these fibres.
  • In mouse peritoneal macrophages, Samples A and B had little effect. Sample C induced release of about 30% LDH and over 60% beta-glucuronidase (BGL).
  • In A549 cell cultures, only Sample C among the tremolite dusts induced giant cells, and it was as active as UICC crocidolite.
  • Toward V79-4 hamster lung cells, Sample A was inert, Sample B was moderately toxic, and Sample C was as toxic as UICC crocidolite.
• The authors' conclusion: The authors suspect, by analogy with the amphibole asbestos minerals, that Tremolite Sample C from South Korea would be a human health hazard if present in sufficient airborne concentration. They reported that an inhalation experiment in rats was being planned.
• Limitations the authors state:
  • The animal data came from two separate experiments using two rat strains. The second experiment had poor survival because of infection.
  • The crocidolite positive control produced far fewer mesotheliomas (6%) than in the authors' earlier experiments with Wistar rats (46% on average). The authors could not exclude chance as the explanation.
  • Because of poor survival, the second experiment had only about 40% of the efficiency of earlier experiments in detecting mesotheliomas.
  • The authors said the data should be interpreted qualitatively rather than quantitatively.

Topics

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

Medical terms in this study, explained in our Lexicon: Tremolite, Amphibole Group, Macrophage, Mesothelioma, UICC, Crocidolite.

Related studies

• Inhalation studies on the effects of tremolite and brucite dust in rats — J.M. Davis, J. Addison, et al. (1985)
• Mesothelioma in Cyprus: the role of tremolite — K. McConnochie, L. Simonato, et al. (1987)
• Metsovo-tremolite asbestos fibres: in vitro effects on mutation, chromosome aberration, cell transformation and intercellular communication — K. Athanasiou, S.H. Constantopoulos, et al. (1992)
• Chronic effects of dietary exposure to amosite asbestos and tremolite in F344 rats — E.E. McConnell, H.A. Rutter, et al. (1983)
• Chrysotile, tremolite, and malignant mesothelioma in man — A. Churg (1988)
• Cohort study of mortality of vermiculite miners exposed to tremolite — J.C. McDonald, A.D. McDonald, et al. (1986)

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