The enigmatic asbestos body: its formation and significance in asbestos-related disease

Our plain-English summary of The enigmatic asbestos body: its formation and significance in asbestos-related disease, by A. Morgan, A. Holmes (Environmental Research, 1985).

The study

• Authors: A. Morgan, A. Holmes
• Journal: Environmental Research
• Published: 1985;38(2):283-92
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

It is well established that many different types of fibre, both organic and inorganic, can become coated with ferritin in lung to give ferruginous bodies. The presence of such bodies is one factor which is taken into account in assessing cases with asbestos-related disease for the purpose of compensation, although their presence is only an indication of past exposure and not proof of the causative role of asbestos. In this paper, evidence relating to the formation of ferruginous bodies in human lung is reviewed, to identify factors which predispose certain types and dimensions of fibre to become coated. Work with experimental animals is also summarised to give some indication of the time course of body formation.

In plain English

This article was a review by two researchers at the Atomic Energy Research Establishment, Harwell, UK. It covered evidence on how asbestos bodies form. These are fibres that become coated in the lung with ferritin, a protein that contains iron. The review drew on post-mortem human lung studies, many of them the authors' own earlier work, and on animal experiments. The studies reviewed found that few bodies were shorter than 10 micrometres and that the chance of a fibre being coated rose with its length. Counted by light microscope, about 10% of amphibole fibres in lung were coated. The authors estimated that the true figure for crocidolite was only about 1%. In hamsters given glass fibres, coating appeared within one to two months, and fibres under 10 micrometres did not become coated. The authors concluded that whether a fibre becomes coated depends mainly, perhaps only, on its size, and needs a diameter somewhat greater than 0.2 micrometres. They wrote that bodies can guide judgments of past exposure to amphiboles, but not to chrysotile or Turkish erionite. They also wrote that the bodies' role in asbestos-related disease is unclear.

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: Review of published evidence (human lung studies and animal experiments), much of it the authors' own earlier work
• Who was studied: No new study population. The review covered earlier findings from post-mortem human lung residues and from animals. Human groups included UK gas mask factory workers exposed to crocidolite, Finnish anthophyllite mine workers, insulation workers, Australian crocidolite miners and members of the US general public. Animals included guinea pigs, mice, hamsters and rats.
• Exposure: Asbestos fibres (the amphiboles crocidolite, amosite, anthophyllite and tremolite, plus chrysotile) and other fibres: erionite and other zeolites, sized glass fibres, and rockwool fibres given to animals
• Main results:
  • In earlier light-microscope studies of human lung, the probability of a fibre becoming coated increased with fibre length. Few bodies shorter than 10 micrometres are normally found in human lung.
  • Counted by light microscope, the proportion of fibres in lung that were coated was generally about 10%, whatever the type of amphibole. For example, an earlier study by the same authors found an average of 11.0% (plus or minus 1.2%, SEM) in 27 gas mask factory workers exposed to crocidolite.
  • Only about one uncoated crocidolite fibre in ten is seen with the light microscope. Allowing for this, the authors estimated that the true proportion of coated crocidolite fibres is only about 1%.
  • The probability of coating for fibres 20 to 40 micrometres long varied between lung regions and between people. It ranged from 14 to 56% within the lower lobe of one insulation worker, and from 6 to 34% in samples from different UK gas mask factory workers.
  • Thicker amphibole fibres such as anthophyllite were coated in a greater proportion than the thinner crocidolite and amosite.
  • In hamsters given sized glass fibres, coating was detected after 1 month at the 60 micrometre length threshold and after 2 months at the 30 micrometre threshold. The comparison symbols are garbled in the scan. Glass fibres under 10 micrometres long did not become coated.
  • In a hamster study with rockwool fibres, the thickest fibres showed no coating even after 1 year.
  • In heavy occupational exposure, asbestos body concentrations in lung may approach 10 to the 8th power per gram dry weight. Values reported for urban populations without occupational exposure were almost always below 10 to the 4th power per gram dry weight.
• The authors' conclusion: The authors concluded that the probability of a fibre becoming coated is determined mainly, and perhaps only, by its dimensions, with diameters somewhat greater than 0.2 micrometres needed. They concluded that bodies can be used as a guide to past exposure to all fibrous amphiboles, but not to chrysotile or other very thin fibres such as Turkish erionite. They also said that whether asbestos bodies have any significance in the development of asbestos-related disease is unclear.
• Limitations the authors state:
  • A similar time course of body formation across several rodent species does not prove that it is as rapid in humans.
  • The probability of coating can be measured most accurately only for fibres 20 to 40 micrometres long. Accuracy falls off for shorter and longer fibres.
  • The light microscope misses most thin fibres. Only about 15% of crocidolite fibres in human lung can be detected with it.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Body Formation, Ferritin, Ferruginous Bodies.

Related studies

• An assessment of asbestos body formation in extrapulmonary sites: liver and spleen — M.G. Williams, R.F. Dodson, et al. (2001)
• Asbestos-body formation in the lungs of rats and guinea-pigs after inhalation of anthophyllite — S.K. Botham, P.F. Holt (1972)
• An electron microscopy study of the effect of asbestos dust on the lung — J.M. Davis (1963)
• The ultrastructure of asbestos bodies from guinea-pig lungs — J.M. Davis (1964)
• Ferritin adsorption on amosite fibers: possible implications in the formation and toxicity of asbestos bodies — B. Fubini, F. Barceló, et al. (1997)
• Formation of the asbestos body. A comparative study with three types of asbestos — Y. Suzuki, J. Churg (1970)

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