The effects of intrapleural injections of alumina and aluminosilicate (ceramic) fibres

Our plain-English summary of The effects of intrapleural injections of alumina and aluminosilicate (ceramic) fibres, by G.H. Pigott, J. Ishmael (International Journal of Experimental Pathology, 1992).

The study

• Authors: G.H. Pigott, J. Ishmael
• Journal: International Journal of Experimental Pathology
• Published: 1992;73(2):137-46
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

Groups of rats, 24 male and 24 female, approximately 8 weeks old, were dosed by a single intrapleural injection with a saline suspension of refractory alumina fibres (Saffil fibres ICI plc) either as manufactured or after extensive thermal ageing; or one of two aluminosilicate ('ceramic') fibres with different diameter distributions. Similar groups were dosed with a suspension of UICC chrysotile A asbestos or saline solution to serve as positive and negative controls respectively. Rats were maintained to 85% mortality and all decedents and terminal sacrifices were closely examined for the presence of mesothelioma. Malignant mesothelioma was diagnosed in ten rats, seven dosed with asbestos and three dosed with aluminosilicate fibre B. No mesothelioma was detected in any rat dosed with Saffil fibres or aluminosilicate fibre A or in negative controls. The results support the predicted inert nature of Saffil alumina fibres and provide further evidence for the importance of fibre dimension in the induction of mesothelioma. The implication of the results for inhalation exposures is discussed.

In plain English

In this animal experiment at ICI's Central Toxicology Laboratory, UK, groups of 24 male and 24 female rats each received one 0.2 ml injection aimed at the chest cavity. The fibre groups received 20 mg of Saffil alumina fibres (as manufactured or heat-aged), aluminosilicate ('ceramic') fibre A or B, or UICC chrysotile A asbestos (positive control); controls received saline only. Two misdosed fibre A rats were excluded. Malignant mesothelioma of the pleura or peritoneum developed in ten rats. Seven had been given chrysotile; all seven tumours were pleural and in males. Three had been given fibre B, an incidence of 6.25%; two of these were peritoneal, in rats with evidence of injection into the abdomen. No malignant pleural or peritoneal mesothelioma occurred in the saline, Saffil, aged Saffil or fibre A groups. The authors judged benign testicular mesotheliomas in one Saffil, two aged-Saffil and four fibre A rats incidental to treatment. They linked mesothelioma to 'fine long' fibres, concluded that Saffil fibres do not present a mesothelioma risk to humans, and noted injection results do not necessarily show an inhalation hazard.

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: a long-term study of a single intrapleural (chest cavity) injection in rats.
• Who was studied: Albino Alpk:AP (Wistar-derived) rats, about 8 weeks old at dosing, at ICI Central Toxicology Laboratory, Alderley Park, UK. There were six groups, each of 24 males and 24 females. Two rats in the aluminosilicate fibre A group were misdosed and excluded, leaving 46. The rats were kept until 85% overall mortality, and the study ended in weeks 122 to 123.
• Exposure: Every rat received a single 0.2 ml intrapleural injection. In the fibre groups, the injection contained 20 mg of suspended solids. The test materials were Saffil alumina fibres as manufactured, Saffil fibres after extensive thermal ageing, aluminosilicate fibre A (made from calcined kaolin clay) and aluminosilicate fibre B (made from alumina and silica). UICC chrysotile A (Rhodesian) asbestos was the positive control. The negative control group received saline only.
• Main results:
  • Malignant mesothelioma of the pleura or peritoneum was found in ten rats: seven of 48 in the chrysotile asbestos group and three of 48 in the aluminosilicate fibre B group. None was found in the saline control, Saffil, aged Saffil or aluminosilicate fibre A groups.
  • In the asbestos-dosed group, all malignant mesotheliomas occurred in males, and all seven were pleural (per Table 5). The earliest tumour in the study was seen 63 weeks after injection.
  • In the aluminosilicate fibre B group, two of the three malignant mesotheliomas were peritoneal. In both of those rats there was evidence that the injection had gone into the abdomen rather than the chest.
  • The mesothelioma incidence in the aluminosilicate fibre B group was 6.25%.
  • Benign testicular mesothelioma (of the tunica vaginalis) was seen in one Saffil-dosed rat, two aged-Saffil-dosed rats and four rats dosed with aluminosilicate fibre A.
  • The authors found that no group's incidence of benign testicular mesothelioma was above historical control values. They regarded these tumours as incidental to treatment.
  • Most asbestos-dosed rats developed nodular pleural plaques. Saffil caused milder pleural changes than asbestos. The aluminosilicate fibres caused a reaction similar to Saffil's but somewhat more severe.
  • Overall mortality was broadly comparable between groups.
  • The authors reported a correlation between the presence of 'fine long' fibres in the samples and the occurrence of mesothelioma.
• The authors' conclusion: The authors concluded that Saffil alumina fibres, both as manufactured and after thermal ageing, do not present a risk of mesothelioma to humans. They also said the results support the importance of fibre dimension in causing mesothelioma.
• Limitations the authors state:
  • The authors stated that injection studies probably reflect a material's intrinsic ability to cause mesothelioma but do not necessarily indicate a hazard from inhalation.
  • In a small proportion of animals in most groups, some or all of the dose went into the abdomen instead of the chest.

Topics

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

Related studies

• An assessment of the fibrogenic potential of two refractory fibres by intraperitoneal injection in rats — G.H. Pigott, J. Ishmael (1981)
• An epidemiological study of the respiratory health of workers in the European refractory ceramic fibre industry — H.A. Cowie, P. Wild, et al. (2001)
• Health effects of refractory ceramic fibres: scientific issues and policy considerations — L.R. Glass, R.C. Brown, et al. (1995)
• Analysis of the biological and chemical reactivity of zeolite-based aluminosilicate fibers and particulates — E. Fach, W.J. Waldman, et al. (2002)
• Mesothelioma in rats following intrapleural injection of chrysotile and phosphorylated chrysotile (chrysophosphate) — A. Van der Meeren, J. Fleury, et al. (1992)
• Pathological characterization of lung fibrosis in Sprague-Dawley rats treated with fluoro-edenite fibres by intrapleural injection — E. Tibaldi, F. Gnudi, et al. (2024)

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