Animal Experiments on Biological Effects of Mineral Fibres

Our plain-English summary of Animal Experiments on Biological Effects of Mineral Fibres, by F. Pott (1980).

The study

• Author: F. Pott
• Published: BIOLOGICAL EFFECTS OF MINERAL FIBRES (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 30., PP 261-272 (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 article was not an original study. It was the author's summary of the papers on animal experiments presented in one session of a conference on the biological effects of mineral fibres, grouped under five headings. The author reported that asbestos fibres produced tumours in several animal species, but rats appeared the most susceptible; other species mostly had longer latent periods and fewer tumours. The summarized work covered how fibres are cleared from and move within the body, fibres crossing the gut, and whether benzo[a]pyrene, N-nitrosodiethylamine, cigarette smoke or radiation added to the effects of asbestos. In one summarized study, intrapleural injection of chrysotile and four man-made mineral fibres gave its highest tumour rate, 12.5%, in the chrysotile group and no tumours with slag wool. The author concluded that a long, thin fibre seemed to have more cancer-causing and scarring potency than a short or thick one. The author added that it was not proven that fibres shorter than 5 micrometres cannot cause tumours or fibrosis. The author called for at least 50 well-defined standard fibre samples.

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: the session chairman's summary of the animal-experiment papers presented at a conference session, grouped under five subject headings
• Who was studied: Animal experiments reported by other research groups, mainly in rats, plus mice, golden hamsters, European hamsters, rabbits and rhesus monkeys
• Exposure: Chrysotile, amosite, crocidolite, tremolite, anthophyllite, talc, attapulgite, glass fibres, slag wool and other man-made mineral fibres. Routes were intrapleural and intraperitoneal injection, intratracheal instillation, inhalation, and feeding or drinking water. Some studies combined fibres with benzo[a]pyrene, N-nitrosodiethylamine, cigarette smoke or radiation.
• Main results:
  • Across the summarized studies, asbestos fibres produced tumours in several species, but rats appeared the most susceptible in latent period and number of tumours.
  • In a summarized study by Wehner, inhaled talc deposited in the alveoli had a biological half-life of seven to ten days. In a study by Morgan et al. (1977), alveolar clearance half-times for chrysotile and amphibole asbestos ranged from 60 to 90 days.
  • In a summarized study by Pott et al., after intratracheal instillation in European hamsters, glass fibres thinner than 0.4 um were found in the diaphragm and spleen in the same range as crocidolite.
  • In a summarized study by Smith et al., golden hamsters were given drinking water containing 1300 million amosite fibres per litre. Among 180 hamsters there were two early squamous-cell carcinomas of the forestomach, one peritoneal mesothelioma and one lung carcinoma, which could not be definitely attributed to the treatment.
  • Pylev's work in the session found that benzo[a]pyrene had no influence on pleural carcinogenesis. Earlier studies cited by the author found that it stimulated the cancer-causing effect of asbestos in the lung after intratracheal instillation.
  • In summarized studies by Johnson & Wagner and Wagner et al., chrysotile and four man-made mineral fibres were injected intrapleurally. Tumour rates were relatively low; the highest, 12.5%, was in the chrysotile group, and slag wool induced no tumours.
  • In summarized hamster experiments by Smith et al. with glass fibres, tumours developed only in groups given samples with a substantial percentage of fibres longer than 20 um.
  • In work by Stanton and colleagues, cited but not presented in the session, intrapleural tests of man-made mineral fibres in rats showed the best correlation with tumour rates for fibres less than 0.25 um in diameter and more than 8 um in length.
  • In summarized studies by Wagner et al. of three Canadian chrysotile samples in rats, UICC chrysotile was the most carcinogenic of the three after inhalation and the least after intrapleural injection.
• The authors' conclusion: The author concluded that a long, thin fibre seems to have more carcinogenic and fibrogenic potency than a short or thick fibre. The author added that it is not proven that fibres shorter than 5 um cannot induce tumours or fibrosis. The author proposed that short fibres may be weakly carcinogenic, but that many short fibres may induce a tumour as easily as a few long ones. The author called for at least 50 well-defined standard samples of asbestos and man-made mineral fibres.
• Limitations the authors state:
  • The author stated that the many results published in recent years could not all be cited.
  • The author stated that many experimenters use self-prepared dusts that are hardly reproducible and poorly characterized, which makes results difficult to compare and interpret.
  • The author stated that it is nearly impossible to obtain two fibre samples that differ in only one property.

Topics

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

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