The ingestion of asbestos fibers

Our plain-English summary of The ingestion of asbestos fibers, by I. Webster (Environmental Health Perspectives, 1974).

The study

• Author: I. Webster
• Journal: Environmental Health Perspectives
• Published: 1974;9:199-202
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Feeding of baboons with crocidolite showed small numbers of asbestos needles 0.5-1 mum in ashed tissue of the gut wall, which probably came from iron-containing macrophages. It is suggested that pleural plaques and hyaline nodules in the peritoneum represent a hypersensitivity reaction to ferritin protein coating on asbestos fibers. In South Africa only a few peritoneal mesotheliomas come from the asbestos areas, and the incidence of gastrointestinal carcinomas is no greater than normal. Intrapleural and intraperitoneal injection produces unrealistic situations. Calcium salts are deposited on asbestos cement pipes from hard water and organic material from soft water. It is difficult to envisage asbestos contamination of the water so reticulated.

In plain English

This 1974 conference paper by I. Webster, of the National Research Institute for Occupational Diseases in Johannesburg, combined laboratory observations in baboons with South African register figures and observations of asbestos-cement water pipes. Baboons in the author's laboratory had eaten food and drunk water contaminated with asbestos, in some cases at heavy concentrations for up to 5 years. None showed a peritoneal or gastrointestinal tumor. In a pilot experiment, one baboon was given 200 mg of crocidolite through a stomach tube. Under the electron microscope, ashed gut tissue showed small asbestos needles of 0.5 to 1 micrometre, which the author judged had in all probability come from iron-containing macrophages. The author reported no evidence of asbestos in the stomach lining. The South African register held some 450 pleural but only 24 peritoneal mesotheliomas. Asbestos-cement pipes carrying hard water showed little change, while acidic sewage corroded them. The author suggested that pleural plaques and peritoneal hyaline nodules may be a hypersensitivity reaction. The author concluded that animal experiments only partly supported epidemiological reports of increased intestinal cancer, and that injecting asbestos into body cavities creates an artificial situation.

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: Conference paper combining animal feeding experiments in baboons (including a one-animal pilot experiment), counts from a South African mesothelioma register, and observations of asbestos-cement pipes
• Who was studied: Laboratory baboons (number not stated, described as 'many'), one of them in a pilot gastric-tube experiment; also cases in the South African Asbestos Tumour Reference Panel Register
• Exposure: Baboons ate food and drank water contaminated with asbestos, some at heavy concentrations for up to 5 years; one baboon received 200 mg of crocidolite asbestos by gastric tube
• Main results:
  • No peritoneal or gastrointestinal tumor was found in any of the baboons fed asbestos-contaminated food and water, and no macroscopic lesion was found in the abdominal cavity
  • In the pilot baboon, asbestos needles were found in the feces on the day of dosing; at autopsy the following Monday they were found only in the lower part of the pelvic colon
  • Macrophages containing iron particles were seen in the mucosa of the duodenum and upper ileum
  • On electron microscopy, ashed tissue showed small asbestos needles 0.5 to 1 micrometre long, which the author judged in all probability came from the iron-containing macrophages; X-ray diffraction confirmed the fibers were asbestos
  • No asbestos particles or needles were found in the mucous membrane of the stomach
  • The South African Asbestos Tumour Reference Panel Register held some 450 pleural mesothelial tumors but only 24 peritoneal mesotheliomas
  • Asbestos-cement pipes carrying hard water showed little change even after many years; with soft water there was little damage and organic material was deposited on the inner surface
  • Sewage, being acid, corrodes asbestos-cement pipes
• The authors' conclusion: The author concluded that animal experimentation only partly supports epidemiological studies showing increased intestinal carcinoma, that an increased incidence of gastric carcinoma is difficult to support, and that direct injection into the peritoneal or pleural cavities creates an artificial situation. The author also suggested that pleural plaques and peritoneal hyaline nodules may be a hypersensitivity reaction to the ferritin protein coating of asbestos fibers.
• Limitations the authors state:
  • The author presented the baboon findings as needing confirmation
  • The author described the biological effects of ingested asbestos as a new field of research

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Macrophage, Pleural Plaques, Peritoneum, Ferritin, Peritoneal Mesothelioma, Carcinoma, Asbestos-Cement.

Related studies

• Asbestos fibers in human pulmonary and extrapulmonary tissues — J. Huang, N. Hisanaga, et al. (1988)
• A preliminary study of biochemical changes in the rat small intestine following long-term ingestion of chrysotile asbestos — R. Jacobs, K.S. Dodgson, et al. (1977)
• Distribution of 6-6(n)-3[H]sucrose and its radiolabeled degradation products from isolated, perfused rat small intestine loops following prolonged ingestion of chrysotile asbestos — R. Jacobs, R.J. Richards (1980)
• Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers — M. Boulanger, F. Morlais, et al. (2015)
• The short-term effects of chronic asbestos ingestion in rats — R.E. Bolton, J.M. Davis (1976)
• Malignant peritoneal mesothelioma in a 76-year-old woman with a history of asbestos fiber ingestion — P. Van Kesteren, J. Bulten, et al. (2004)

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