The Effect of Length on the Clearance of Fibres from the Lung and on Body Formation

Our plain-English summary of The Effect of Length on the Clearance of Fibres from the Lung and on Body Formation, by A. Morgan (1980).

The study

• Author: A. Morgan
• Published: BIOLOGICAL EFFECTS OF MINERAL FIBRES (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 30., PP 329-335 (1980)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This paper examined how fibre length affects lung clearance of asbestos fibres and the formation of coated fibres ("bodies"). Rats inhaled UICC anthophyllite asbestos and were killed at various times up to two years later. Fibres left in their lungs were counted and sized under an optical microscope. One day after exposure, fibre lengths in the lung were similar to those in the airborne dust. Later, the share of fibres shorter than 5 micrometres fell steadily, which the author read as showing that shorter fibres were cleared more efficiently. The lungs of three gas-mask factory workers exposed to Australian crocidolite during the Second World War were also examined. Only about 10 percent of their uncoated fibres were shorter than 5 micrometres, and 20 to 30 percent were longer than 20 micrometres. In the rats, virtually all fibres longer than 80 micrometres were coated. The author concluded that longer fibres were more likely to become coated. The author also suggested, from preliminary results needing further work, that thin fibres may be coated less readily than thicker fibres of the same length.

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 inhalation experiment in rats, plus measurement of fibres in lung tissue from three exposed workers
• Who was studied: Rats killed at various times up to two years after exposure (number not given in the text), and the lungs of three gas-mask factory workers (lung tissue supplied from Broadgreen Hospital, Liverpool, UK)
• Exposure: Rats: UICC anthophyllite asbestos by inhalation (dose not given in the text). Workers: Australian crocidolite asbestos during the Second World War in gas-mask manufacture
• Main results:
  • In rats, fibres shorter than 5 micrometres made up a progressively smaller share of lung fibres after the first day, and longer categories a larger share
  • In rats, fibres shorter than 5 micrometres were cleared from the lung more efficiently than longer fibres
  • In the three gas-mask workers, uncoated fibre length distributions were similar, and only about 10 percent of uncoated fibres were shorter than 5 micrometres (confirmed by electron microscopy)
  • In the three gas-mask workers, between 20 and 30 percent of uncoated fibres were longer than 20 micrometres
  • In rats killed after 100 days, most coated fibres fell in the 40 to 80 micrometre category, and virtually all fibres longer than 80 micrometres were coated
  • In the gas-mask workers, few coated fibres were shorter than 10 micrometres
• The authors' conclusion: The author concluded that short fibres (particularly under 5 micrometres) are cleared relatively efficiently, and that the longer a fibre, the greater the probability of body formation. The author suggested that failure of the lung to coat long, thin crocidolite fibres could help account for crocidolite's carcinogenicity relative to the thicker amosite and anthophyllite, but stated that further work is required.
• Limitations the authors state:
  • Optical microscopy could not detect the thinnest fibres, so the fibre concentrations reported for the human lungs are underestimates
  • Little information exists on the airborne fibres to which workers were exposed many years ago
  • The finding that thin fibres of a given length are coated less readily than thicker fibres of the same length is preliminary and needs further work

Topics

Medical terms in this study, explained in our Lexicon: UICC, Anthophyllite, Crocidolite.

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