Cytotoxicity of a short-fiber chrysotile asbestos for human alveolar macrophages: preliminary observations

Our plain-English summary of Cytotoxicity of a short-fiber chrysotile asbestos for human alveolar macrophages: preliminary observations, by H. Yeager, D.A. Russo, M. Yañez, et al (Environmental Research, 1983).

The study

• Authors: H. Yeager, D.A. Russo, M. Yañez, D. Gerardi, R.P. Nolan, E. Kagan, A.M. Langer
• Journal: Environmental Research
• Published: 1983;30(1):224-32
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Studies were performed to compare the cytotoxicity for human alveolar macrophages of a naturally occurring short-fiber chrysotile asbestos (RG 144) to that of a standard reference mixed-fiber (long and short) chrysotile asbestos (UICC chrysotile A. Rhodesian). Parallel studies were also performed with quartz (Min-U-Sil 15), a known macrophage toxin. On a mass basis, and after 24 hr incubation, RG 144 was more cytotoxic than the UICC standard reference fiber and less toxic than quartz (silica). The cytotoxic potential of RG 144 chrysotile was further enhanced after size reduction by milling. These findings may have important biologic implications with respect to the use of short-fiber asbestos in industry.

In plain English

This laboratory study tested chrysotile asbestos on alveolar macrophages, lung immune cells collected by lung washing from seven healthy volunteers aged 21 to 26. The cells were exposed for one hour to 50 or 100 micrograms per culture of one of three materials. The first was a standard chrysotile with long and short fibers (UICC chrysotile A, Rhodesian), in which about 25% of fibers were longer than 5 micrometers. The second was a naturally short-fiber chrysotile from California, RG 144, in which 2% were longer than 5 micrometers; it was tested unmilled or milled for 60 or 1200 seconds. The third was quartz. Cell survival was counted 24 hours later. Survival was 88.3% without dust. At 50 and 100 micrograms it was 67.2% and 62.7% with UICC chrysotile, 47.4% and 42.0% with unmilled RG 144, 23.7% and 14.4% with RG 144 milled for 1200 seconds, and 29.3% and 9.3% with quartz. No clear dose-response was seen. The authors noted their short fiber might not represent all short-fiber chrysotile. They concluded that further study of its possible harmful effects should be pursued.

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) experiment on human lung cells; cell death measured by trypan blue dye exclusion
• Who was studied: Alveolar macrophages obtained by bronchoscopy and lung lavage from seven healthy volunteers aged 21 to 26 at Georgetown University Medical Center, Washington, D.C.; one volunteer was lavaged twice and another three times. Dates of collection are not given.
• Exposure: UICC chrysotile A (Rhodesian), with about 25% of fibers longer than 5 micrometers. RG 144 (Calidria), a naturally short-fiber chrysotile from the New Idria deposit in California, with 2% of fibers longer than 5 micrometers, tested unmilled and after 60 or 1200 seconds of milling. Quartz (Min-U-Sil 15). Doses were 50 and 100 micrograms per culture. Particles were applied for a 1-hour pulse, followed by 24 hours of incubation in fresh medium.
• Main results:
  • Macrophages with no dust: 88.3% viability at both dose columns (10 runs).
  • Macrophages exposed to UICC chrysotile A: 67.2% viability at 50 micrograms and 62.7% at 100 micrograms per culture (10 runs).
  • Macrophages exposed to unmilled RG 144 chrysotile: 47.4% viability at 50 micrograms and 42.0% at 100 micrograms per culture (10 runs). The authors reported that unmilled RG 144 was more cytotoxic than the UICC preparation.
  • Macrophages exposed to RG 144 milled for 60 seconds: 39.7% and 27.4% viability (6 runs). With RG 144 milled for 1200 seconds: 23.7% and 14.4% viability (6 runs). The difference between the two milled preparations was reported as significant (P less than 0.005).
  • Macrophages exposed to quartz: 29.3% viability at 50 micrograms and 9.3% at 100 micrograms per culture (10 runs).
  • The no-dust, UICC chrysotile, unmilled RG 144 and quartz groups all differed significantly from each other (P less than 0.05).
  • The added cytotoxicity of milled RG 144 tracked the number of short fibers and the total fiber number, not the number of fibers longer than 5 micrometers per microgram. The number of long fibers per microgram was virtually identical in the UICC and unmilled RG 144 samples.
  • Viability fell at the higher dose, but no clear dose-response relationship was observed.
• The authors' conclusion: The authors concluded that the naturally occurring short-fiber chrysotile RG 144 is cytotoxic to human alveolar macrophages in vitro. Because this type of short fiber was then in use in the United States, they said further studies of its possible harmful effects should be pursued.
• Limitations the authors state:
  • No clear dose-response was seen. The authors suggested that particle clumping, removal of particles after 1 hour, or protein adsorption onto particles may have modified toxicity at higher doses.
  • Macrophages may take up different fiber sizes differently, which is a possible source of bias.
  • The short fiber tested may be unique and not representative of all short-fiber chrysotile.
  • The findings disagree with other studies. Differences in culture systems and doses may explain the discrepancy.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Santa Rita mine, Joaquin Ridge near Coalinga, California

All asbestos mines

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, Alveolar Macrophage, UICC, Macrophage.

Related studies

• Pulmonary reaction to long and short asbestos fibers is independent of fibroblast growth factor production by alveolar macrophages — I.Y. Adamson, D.H. Bowden (1990)
• Leaching of chrysotile asbestos in human lungs. Correlation with in vitro studies using rabbit alveolar macrophages — M.C. Jaurand, J. Bignon, et al. (1977)
• Phagocytosis of asbestos fibers by human pulmonary alveolar macrophages — T. McLemore, M. Corson, et al. (1979)
• Cytotoxic effects of quartz and chrysotile asbestos: in vitro interspecies comparison with alveolar macrophages — J. Schimmelpfeng, A. Seidel (1991)
• In vitro biodegradation of chrysotile fibres by alveolar macrophages and mesothelial cells in culture: comparison with a pH effect — M.C. Jaurand, A. Gaudichet, et al. (1984)
• Effects of chrysotile on a lysosomal enzyme preparation and on the hydrolytic enzyme activity of cultured alveolar macrophages — R. Desai, R.J. Richards (1983)

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