Cell toxicity, hemolytic action and clastogenic activity of asbestos and its substitutes

Our plain-English summary of Cell toxicity, hemolytic action and clastogenic activity of asbestos and its substitutes, by K. Koshi, N. Kohyama, T. Myojo, et al (Industrial Health, 1991).

The study

• Authors: K. Koshi, N. Kohyama, T. Myojo, K. Fukuda
• Journal: Industrial Health
• Published: 1991;29(2):37-56
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The cell toxicity, hemolytic and clastogenic activity were examined in various kinds of asbestos and some asbestos substitutes with reference to the their mineralogical and physicochemical characteristics. There were thirty-five fibrous and non-fibrous samples including UICC chrysotile, size-selected samples of UICC chrysotile, chrysotile altered by heating and grinding, Yamabe (Japan) chrysotile with long and short fibers, Coalinga (U.S. A.) chrysotile with short fibers, UICC crocidolite, amosite, and 19 non-asbestos samples such as, glass fibers, calcium silicates, sepiolites and some clay minerals. The cell toxicity and the hemolytic and clastogenic activity of asbestos were the strongest for chrysotile among all of the asbestos samples tested, and their strengths varied with fiber length and with the conditions of grinding and heating. These cellular effects of Yamabe chrysotile with long fibers and size-selected UICC chrysotile with long fibers were stronger than those of chrysotile of the same origin but with short fibers. These effects were weaker in chrysotile altered by heating and grinding. Among the asbestos substitutes, the cell toxicity, hemolytic and clastogenic activities of thin glass fibers were more marked than those of thick glass fibers. The four types of sepiolite were strongly hemolytic, but their cell toxicity and clastogenicity varied according to their grade of crystallinity and/or fiber size. These effects of calcium silicates and some clay minerals were generally low but varied with mineral species. In general, the cell toxicity, hemolytic and clastogenic activities of the asbestos substitutes tested here were mild compared with those of asbestos.

In plain English

This was a laboratory (test-tube) study. The authors tested 35 fibrous and non-fibrous mineral samples. These included chrysotile from Canada (UICC), California (Coalinga) and Japan (Yamabe), and UICC amosite and crocidolite. They also included chrysotile sorted by fiber length or altered by heating and grinding, and substitutes such as glass fibers, calcium silicates, sepiolites and clay minerals. They measured the dust dose that halved the ability of Chinese hamster lung cells to form colonies and the dose that burst half of the human red blood cells, and they counted chromosome abnormalities in exposed cells. Among the UICC asbestos samples, chrysotile was the most toxic to cells and the most damaging to chromosomes. Long-fiber chrysotile had stronger effects than short-fiber chrysotile from the same source. Chrysotile ground for 2 hours was much less toxic to cells and caused no structural chromosome damage. Thinner glass fibers had stronger effects than thicker ones, and the four sepiolites differed widely. The authors concluded that the substitutes tested were generally milder than asbestos. They noted it is difficult to judge directly from cell effects whether a dust causes fibrosis or cancer.

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 survival (colony-forming) tests and chromosome tests in Chinese hamster lung cells, and red blood cell bursting (hemolysis) tests with human blood
• Who was studied: 35 fibrous and non-fibrous mineral samples, tested on a Chinese hamster lung (CHL) cell line and on human red blood cells; no people or animals were studied
• Exposure: UICC chrysotile; length-sorted UICC chrysotile; chrysotile altered by heating (600 and 800 degrees C) and ball-mill grinding; long- and short-fiber Yamabe (Japan) chrysotile; short-fiber Coalinga (U.S.A.) chrysotile; UICC crocidolite; amosite; and 19 non-asbestos samples (glass fibers, calcium silicates, sepiolites, clay minerals)
• Main results:
  • Among the UICC reference asbestos samples, chrysotile was the most toxic to the hamster lung cells, followed by amosite and crocidolite. The doses needed to cut colony formation by 50% (lower means more toxic) were 1.6 µg/ml for chrysotile A, 1.2 for chrysotile B, 4.5 for amosite and 7 for crocidolite.
  • Long-fiber Yamabe chrysotile was more toxic to cells than short-fiber Yamabe chrysotile. The 50% toxic dose was 0.2 µg/ml for long fibers and 3.7 µg/ml for short fibers.
  • In length-sorted UICC chrysotile B, the short-fiber fraction was least toxic and toxicity rose with fiber length. The 50% toxic doses were 0.3 µg/ml for the long-residue fraction, 0.9 for the middle fraction and 1.1 for the short fraction.
  • Chrysotile ground for 2 hours had a 50% toxic dose of 25 µg/ml, compared with 1.2 µg/ml for unaltered UICC chrysotile B.
  • The 50% toxic doses of glass fiber codes 100, 104, 108A and 108B were 10, 11, 18 and 27 µg/ml. These codes run from the thinnest to the thickest nominal diameter.
  • Sepiolite from China had a 50% toxic dose of 0.9 µg/ml, which the authors described as the same level as UICC chrysotile. The other sepiolites were less toxic: Kuzuu 2.5, Turkey 30 and Spain 50 µg/ml.
  • Less than 200 µg/ml of UICC chrysotile A and B, long-fiber Yamabe chrysotile and Coalinga chrysotile was needed to burst 50% of red blood cells. UICC amosite and crocidolite rarely reached 50% at any concentration tested.
  • Among the substitutes, sepiolites were the most hemolytic. The 50% hemolytic doses were 110 µg/ml for Kuzuu, 195 for Spain and 210 for Turkey; the China sepiolite was least hemolytic, at 350.
  • The thinnest glass fiber (code 100) had a 50% hemolytic dose of 800 µg/ml. The thicker glass fibers were above 1000 µg/ml.
  • Among the UICC asbestos samples, chrysotile caused the most chromosome damage, followed by crocidolite and amosite.
  • In length-sorted UICC chrysotile, the long-residue fraction caused the most chromosome damage, followed by the middle and short fractions. The short fraction caused only gaps and low levels of polyploidy.
  • Short-fiber Yamabe chrysotile and Coalinga chrysotile did not significantly increase serious chromosome abnormalities. They mainly increased chromatid gaps and polyploidy. Long-fiber Yamabe chrysotile caused breaks, dicentrics, exchanges and rings.
  • Chrysotile ground for 2 hours caused no structural chromosome abnormalities, only low levels of polyploidy.
  • Glass fiber codes 100 and 104 did not significantly increase structural chromosome aberrations but caused relatively high polyploidy. Code 108A caused neither, up to 30 µg/ml.
  • Sepiolites from Kuzuu, Spain and Turkey did not significantly increase chromosome changes up to 100 µg/ml. Sepiolite from China caused relatively high polyploidy, about the same as glass fiber code 100.
• The authors' conclusion: The authors concluded that, in general, the cell toxicity, hemolytic and chromosome-damaging activities of the asbestos substitutes tested were mild compared with those of asbestos.
• Limitations the authors state:
  • The authors stated that it seems difficult to infer whether asbestos causes fibrosis or cancer directly from its effects on cells.

Topics

Medical terms in this study, explained in our Lexicon: UICC, Chrysotile, Crocidolite, Amosite, Silicate, Sepiolite, Fiber Length.

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