Some observations on the in vitro cytotoxicity of chrysotile prepared by the wet dispersion process

Our plain-English summary of Some observations on the in vitro cytotoxicity of chrysotile prepared by the wet dispersion process, by I.P. Gormley, R.E. Bolton, G.M. Brown, et al (Environmental Health Perspectives, 1983).

The study

• Authors: I.P. Gormley, R.E. Bolton, G.M. Brown, J.M. Davis, A. Wright
• Journal: Environmental Health Perspectives
• Published: 1983;51:35-9
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Samples of the chrysotile taken during and after treatment by the wet dispersion process have been tested for their cytotoxic effect in vitro and the results compared with both a UICC chrysotile A sample and a dust prepared from a standard chrysotile textile yarn. Results were obtained from three different in vitro assay systems utilizing P388D1, V79-4 and A549 cells. A sample which still contained the wetting agent used in the wet dispersion process failed to show activity in any of these assays. The other samples, however, were all active with those dusts obtained by milling the final product and by sampling the air of the factory consistently proving significantly more cytotoxic than the standard chrysotile controls. Preliminary results from a parallel in vivo study suggest that these samples are also more active in producing mesotheliomas in rats.

In plain English

This laboratory study, from the Institute of Occupational Medicine in Edinburgh, tested whether chrysotile made into yarn by the 'wet dispersion' process was more damaging to cells than standard chrysotile. Five wet-dispersed chrysotile samples were compared with UICC chrysotile A and with dust from standard chrysotile yarn in three cell-culture tests. The five included milled finished yarn, a sample still containing the process's wetting agent, a heat-cleaned sample, and dust collected from factory air. The sample still containing wetting agent was the least active of the wet-dispersed samples in all three tests. Milled wet-dispersed yarn and factory dust were more toxic to cells than both standard chrysotile samples in all three tests. In preliminary results from rats injected in the abdomen with 25 mg of each dust, the average time to the first 15 mesotheliomas was 276 to 300 days with three wet-dispersed samples, against 354 to 357 days with the standard chrysotiles. Heat-cleaned dust took 367 days. The authors noted the animal work was unfinished. They concluded that dust from wet-dispersed chrysotile may be more dangerous than similar amounts of standard chrysotile dust.

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 study: in vitro cytotoxicity tests in three cell lines, with preliminary results from a parallel animal experiment (intraperitoneal injection in rats)
• Who was studied: Three permanent cell lines grown in culture: P388D1 (described as a mouse macrophage-like cell line), V79-4 and A549 cells. In the animal part, each of the seven dust samples was injected into a group of 32 ten-week-old male Wistar rats. The work was done at the Institute of Occupational Medicine, Edinburgh, Scotland.
• Exposure: Five wet-dispersed chrysotile (WDC) samples: the original experimental sample; milled finished yarn from a long-running factory process (milled WDC); a sample from that process with the wetting agent not removed (unextracted WDC); a sample with the wetting agent removed by heat cleaning (heat-cleaned WDC); and dust from the air of the factory producing the yarn (factory WDC). These were compared with UICC chrysotile A and with dust from a standard chrysotile textile yarn made from the same type of chrysotile (milled chrysotile). Doses were 10 and 50 micrograms per mL in the P388D1 assay, 25 and 50 micrograms per mL in the A549 assay, and 25 mg injected intraperitoneally in rats.
• Main results:
  • P388D1 assay: four of the five WDC samples were more cytotoxic than UICC chrysotile A. The exception was unextracted WDC.
  • P388D1 assay: heat-cleaned WDC, milled WDC and factory WDC were always the most cytotoxic, regardless of time or dose. They reduced cell viability to about half of that seen with UICC chrysotile A. For example, at 48 hours and 50 micrograms per mL, viability as a percentage of the titanium dioxide control was 6 ± 1 (heat-cleaned WDC), 8 ± 2 (milled WDC) and 10 ± 3 (factory WDC), against 21 ± 5 (UICC chrysotile A) and 59 ± 7 (unextracted WDC).
  • V79-4 assay: the dose causing a 50% reduction in cloning efficiency (lower means more toxic) was 87.0 ± 19.1 micrograms of dust for unextracted WDC, the least cytotoxic. It was 5.0 ± 3.4 for milled WDC and 8.4 ± 5.9 for factory WDC, the most cytotoxic. Other values: UICC chrysotile A 13.5 ± 5.6, milled chrysotile 9.7 ± 4.6, heat-cleaned WDC 20.4 ± 15.8, original WDC 46.2 ± 39.2.
  • A549 giant cell assay (a single representative experiment, 100 cells measured per sample): unextracted WDC had the least effect. The other four WDC samples caused more giant cell formation than UICC chrysotile A or milled chrysotile. At 50 micrograms per mL, the share of cells larger than 25 micrometres was 56% (milled WDC), 43% (heat-cleaned WDC), 38% (original WDC), 37% (factory WDC), 31% (UICC chrysotile A), 28% (milled chrysotile) and 8% (unextracted WDC).
  • Across all three assays, factory WDC and milled WDC were more cytotoxic than the standard chrysotile samples.
  • Preliminary rat data: mean induction time for the first 15 mesotheliomas in each group was 276 days (original WDC), 282 days (factory WDC) and 300 days (milled WDC). This compared with 354 days (UICC chrysotile A), 355 days (unextracted WDC), 357 days (milled chrysotile) and 367 days (heat-cleaned WDC).
  • For two samples the rat results did not match the cell results. Heat-cleaned WDC, active in vitro, had the longest tumor induction time. Unextracted WDC, the least active in vitro, produced mesotheliomas after about the same time as the standard chrysotile samples.
• The authors' conclusion: The authors concluded that, although wet-dispersed chrysotile products may give off relatively little respirable dust, any dust that is produced from wet-dispersed chrysotile may be more dangerous than similar amounts of standard chrysotile dust. As a possible explanation, they suggested that the bonding between fibrils may weaken in biological fluids, releasing more individual fibrils.
• Limitations the authors state:
  • The animal results were preliminary. A full comparison of the animal and cell results could not be made until the animal experiments were completed.
  • The unextracted WDC sample was difficult to suspend for the cell tests, and the fibers may not have been fully separated.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, UICC, A549 Cells, Mesothelioma.

Related studies

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• Effects of nonfibrous minerals in the V79-4 cytotoxicity test — G.H. Pigott, P.J. Pinto (1983)
• Influence of crystallization habit of minerals on in vitro cytotoxicity — L.D. Palekar, C.M. Spooner, et al. (1979)
• Cytotoxicity and multinucleate giant cell formation in Chinese hamster lung fibroblast caused by crocidolite and chrysotile — Y.C. Hong, S.S. Choi (1997)
• Cytotoxic action of mineral dusts on CHV 79 cells in vitro: factors affecting toxicity — S.O. Lock, M. Chamberlain (1983)
• Cytotoxicity assessment of some carbon nanotubes and related carbon nanoparticle aggregates and the implications for anthropogenic carbon nanotube aggregates in the environment — L.E. Murr, K.M. Garza, et al. (2005)

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