The Cytotoxicity of UICC and Modified Asbestos In Vitro

Our plain-English summary of The Cytotoxicity of UICC and Modified Asbestos In Vitro, by I.P. Gormley, A. Wright, P. Collings, et al (1980).

The study

• Authors: I.P. Gormley, A. Wright, P. Collings, J.M.G. Davis
• Published: BIOLOGICAL EFFECTS OF MINERAL FIBRES (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 30., PP 427-434 (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 laboratory study from Edinburgh's Institute of Occupational Medicine tested how damaging eleven dust samples were to cells grown in culture. The samples were amosite, crocidolite and chrysotile asbestos, from UICC reference stocks and from factories, including chrysotile heated to 850°C and a wet-dispersed chrysotile, plus a ceramic aluminium silicate fibre. The authors exposed a permanent line of macrophage-like cells (P388D) to 10 and 50 micrograms per millilitre for 24 and 48 hours. They also measured damage to sheep red blood cells (haemolysis) and fibre lengths. All chrysotile samples caused extensive haemolysis and cell damage, while the amphibole and ceramic samples showed little. Heating chrysotile markedly reduced both effects, and wet-dispersed chrysotile was the most cytotoxic. Cell damage rose with dose and time for all samples except the almost inert ceramic. The chrysotile samples whose lengths could be measured had similar length distributions, so the authors could not relate length to cytotoxicity for chrysotile. Wet-dispersed chrysotile formed clumps and could not be measured accurately. They saw some relationship for amosite. In a separate rat injection study from the same laboratory, cytotoxicity matched mesothelioma production for some samples but not for many others.

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: in vitro laboratory experiment (cell culture cytotoxicity tests and red blood cell haemolysis tests)
• Who was studied: Eleven dust samples (listed in Table 1) tested on a permanent line of macrophage-like cells (P388D) and on sheep erythrocytes, at the Institute of Occupational Medicine, Edinburgh. Dates are not given.
• Exposure: UICC amosite (bulk and elutriated), factory amosite, ceramic fibre (aluminium silicate), UICC crocidolite, UICC chrysotile (bulk and elutriated), commercial chrysotile heated to 850°C and its unheated parent sample, factory chrysotile, and wet-dispersed commercial chrysotile. Cells were exposed to 10 and 50 micrograms per millilitre for 24 and 48 hours.
• Main results:
  • All the amphibole samples and the ceramic fibre showed little or no haemolytic ability. Only the bulk UICC amosite sample caused measurable haemolysis (2.7%).
  • All chrysotile samples caused extensive haemolysis. Heated chrysotile was the least haemolytic and elutriated UICC chrysotile was the most haemolytic (85%, standard deviation 5.4).
  • Results in the P388D cells generally agreed with the haemolysis results. The amphibole and ceramic samples showed little haemolytic or cytotoxic activity.
  • Heating a chrysotile sample to 850°C markedly decreased its haemolytic and cytotoxic potential.
  • UICC chrysotile collected from an experimental dust cloud (elutriated) was slightly less cytotoxic but more haemolytic than the UICC chrysotile prepared from bulk material.
  • Wet-dispersed chrysotile was the most cytotoxic dust, clearly so at the 10 micrograms per millilitre dose.
  • Damage to P388D cells increased with time and dose for all samples except the ceramic fibre, which was almost inert. Even the amphibole samples caused some cytotoxicity at 50 micrograms per millilitre for 48 hours.
  • Fibre lengths of wet-dispersed chrysotile could not be measured accurately, because the fibres formed aggregates that ultrasonic treatment could not break up.
  • The bulk UICC amosite sample had a higher proportion of long fibres. It was slightly more haemolytic than the other amosite samples and was the most cytotoxic amosite after 48 hours.
  • No evidence was found for a specific release of lysosomal enzymes from the cells.
  • In a parallel study in the same laboratory, the same dusts were injected into the abdominal cavity (intraperitoneally) of rats. Wet-dispersed chrysotile produced tumours several months earlier than any other dust. Heated chrysotile produced tumours later than the other dusts and in fewer animals.
• The authors' conclusion: The authors concluded that the two test systems generally agreed, with the amphibole samples less cytotoxic and haemolytic than the chrysotile samples. For chrysotile, cytotoxicity could not be correlated with fibre length because the length distributions were similar, but some relationship was seen with amosite. In vitro cytotoxicity agreed with mesothelioma production in rats for some samples but not for many others.
• Limitations the authors state:
  • The study gave little information on the effect of fibre length for chrysotile, because all the chrysotile samples had similar length distributions.
  • The result for wet-dispersed chrysotile is a conservative estimate, because the material was hard to disperse and re-aggregated in the cultures.
  • The fibre length distribution of wet-dispersed chrysotile could not be measured accurately.
  • In the rat study, the 25 mg dose was probably too high to separate the effects of closely related dusts. Results for the aluminium silicate fibres were not yet available.
  • The tumour studies need repeating over a range of doses to see whether the link between cytotoxicity and tumour production holds for all dusts.

Topics

Medical terms in this study, explained in our Lexicon: UICC, Amosite, Crocidolite, Chrysotile, Silicate, Macrophage, Amphibole Group, Mesothelioma.

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