Effects of nonfibrous minerals in the V79-4 cytotoxicity test

Our plain-English summary of Effects of nonfibrous minerals in the V79-4 cytotoxicity test, by G.H. Pigott, P.J. Pinto (Environmental Health Perspectives, 1983).

The study

• Authors: G.H. Pigott, P.J. Pinto
• Journal: Environmental Health Perspectives
• Published: 1983;51:173-9
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The use of the V79-4 system as a primary screen for fiber carcinogenicity is dependent on the observed correlation between cytotoxicity of the test material in the system and mesothelioma following intrapleural injection in animals. This correlation has been established for relatively pure samples of fibrous minerals. The wider application of the system as a screen for industrial dusts may depend on the ability of the system to show an unequivocal response to small yet significant percentages of fibrous dust in the presence of a large excess of nonfibrous material. Some materials tested, including platy minerals, show a response in the test which, while clearly less than that from UICC asbestos samples, could be construed as a positive result. Some, though not all, of these minerals show a nonlinear dose response in the test. This anomalous dose response may aid in the identification of some false positive results but the variety of responses to nonfibrous minerals places a limit on the predictive value of the test mixtures. Results obtained from mixtures of "standard" dust samples suggest this limit is reached at or above 10% fibrous content. Such levels would be significant in terms of human exposure. Extension of the concentration range tested does not improve the predictive value of the test.

In plain English

This was a laboratory study of Chinese hamster lung cells (the V79-4 cell line) grown in culture. The authors exposed the cells to mineral dusts and counted how many cells survived to form colonies. They tested UICC crocidolite asbestos, several forms of silica, mica minerals (biotite, muscovite, phlogopite, hydrophlogopite), talc and calcium carbonate. They also tested mixtures of crocidolite with calcium carbonate, South African quartz or biotite. Crocidolite was highly toxic to the cells, although its strength varied between preparations. Most nonfibrous dusts showed little toxicity, but some silica samples and muscovite showed an unusual two-stage response. In the mixtures, the crocidolite drove the toxicity, and at 10% crocidolite the mixture's toxicity approached that of the other dust alone. When doses were raised to 1000 micrograms per mL, the other dusts varied too widely to allow prediction in blind testing. Even so, 5% crocidolite could be detected in calcium carbonate. The authors concluded that the test does not by itself offer a satisfactory screen for mixed dusts, because a detection limit of about 10% asbestos is not satisfactory.

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: Laboratory (in vitro) cell culture experiment: a cytotoxicity test measuring how many cells survived to form colonies after exposure to dust
• Who was studied: V79-4 Chinese hamster lung cells grown in culture, obtained from the MRC Pneumoconiosis Research Unit, Penarth, UK
• Exposure: Single dusts: UICC crocidolite asbestos; alpha-quartz (Min-U-Sil and a South African sample), cristobalite and amorphous (precipitated) silica; the mica minerals biotite, muscovite, phlogopite and hydrophlogopite; talc; and calcium carbonate (marble chippings). Mixtures: UICC crocidolite diluted with calcium carbonate, South African quartz or biotite, at various ratios. Concentrations were tested up to 100 micrograms per mL, and in further experiments up to 1000 micrograms per mL.
• Main results:
  • UICC crocidolite was highly cytotoxic to the cells. Different stock suspensions made from the same sample varied: the concentration causing a 50% reduction in plating efficiency (CD50) ranged from 7 to 30 micrograms per mL.
  • Phlogopite, hydrophlogopite and biotite each showed a similar minimal response, with a CD50 above 100 micrograms per mL.
  • Talc was somewhat more cytotoxic than these micas. Muscovite gave a different response, resembling that of Min-U-Sil quartz.
  • Silica samples that were significantly cytotoxic showed a two-stage (biphasic) response. This was clearest with amorphous silica. The cristobalite sample was practically inert.
  • Calcium carbonate was not cytotoxic in the test.
  • In mixtures, the total cytotoxicity approached that of the diluent dust alone at a level of 10% crocidolite, for each of the three diluents.
  • None of the diluents enhanced or suppressed the cytotoxic effect of crocidolite in the mixtures.
  • When the concentration range was extended to 1000 micrograms per mL, the diluent dusts alone varied so widely in cytotoxicity that no prediction could be made for blind testing of mixtures.
  • In calcium carbonate and crocidolite mixtures at the extended range, 5% crocidolite could be detected, even with the less cytotoxic crocidolite suspension.
• The authors' conclusion: The authors concluded that the V79-4 test does not by itself offer a satisfactory primary screen for mixed dusts, because a detection limit of about 10% asbestos would not be satisfactory. They added that it may be more sensitive when the mixture's components are known, for example a highly cytotoxic fiber in an essentially inert diluent, where a detection limit of 5% or less is readily achieved.
• Limitations the authors state:
  • Cell survival in the test depended on which batch of fetal bovine serum was used.
  • Different stock suspensions prepared from the same crocidolite sample gave different cytotoxicity.
  • At the higher concentrations, repeat experiments were less consistent.
  • The reason for the unusual dose response seen with some silica forms and muscovite was not determined.

Topics

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

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

Related studies

• Cytotoxic action of mineral dusts on CHV 79 cells in vitro: factors affecting toxicity — S.O. Lock, M. Chamberlain (1983)
• Influence of crystallization habit of minerals on in vitro cytotoxicity — L.D. Palekar, C.M. Spooner, et al. (1979)
• Comparative effects of fibrous and nonfibrous minerals on cells and liposomes — C.D. Woodworth, B.T. Mossman, et al. (1982)
• Effect of mineral dusts on metabolic cooperation between Chinese hamster V79 cells in vitro — M. Chamberlain (1983)
• Some observations on the in vitro cytotoxicity of chrysotile prepared by the wet dispersion process — I.P. Gormley, R.E. Bolton, et al. (1983)
• The cytotoxic effects of asbestos and other mineral dust in tissue culture cell lines — M. Chamberlain, R.C. Brown (1978)

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