Physical and microchemical alterations of chrysotile and amosite asbestos in the hamster lung

Our plain-English summary of Physical and microchemical alterations of chrysotile and amosite asbestos in the hamster lung, by G. Kimizuka, N.S. Wang, Y. Hayashi (Journal of Toxicology and Environmental Health, 1987).

The study

• Authors: G. Kimizuka, N.S. Wang, Y. Hayashi
• Journal: Journal of Toxicology and Environmental Health
• Published: 1987;21(3):251-64
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The physical and microchemical alterations of chrysotile and amosite asbestos (Union International Contre le Cancer standard samples) in the hamster lung and in vitro following acid treatments were studied by scanning electron microscopy (SEM) and x-ray energy-dispersive spectrometry (XEDS). Following intratracheal instillation, the ratio of short chrysotile fibers (less than 5 microns in length) decreased initially from 38% to 13% in the hamster lung, but increased again to 56% 2 years after the instillation. The majority of these new short chrysotile fibers had diameters less than 0.05 micron. Contrary to this, short amosite fibers (less than 5 microns in length) decreased from 41% initially to 4% 2 yr after instillating into the hamster lung. The diameters of amosite fibers appeared much less altered than that of chrysotile during the same time period. After 2 yr in the hamster lung, 33% of chrysotile and 68% of amosite found were asbestos bodies. The Si/Mg ratios of chrysotile fibers with diameters less than 0.2 micron were significantly higher than those with diameters between 0.2 and 0.6 micron in all groups: this relationship was reversed in all amosite groups. The Si/Mg ratios of the instillated and acid-treated chrysotile fibers were both higher than that of the same-sized control fibers. Acid treatments of chrysotile fibers in asbestos bodies from the hamster lung further altered their Si/Mg ratio. The Si/Mg ratios of the instillated amosite fibers were lower than that of the same-sized control fibers, but the difference between them disappeared following acid treatments. The hamster lung disposed of both chrysotile and amosite fibers smaller than 5 microns efficiently. Chrysotile and its asbestos bodies appeared to lose Mg ions and to fragment continuously in the hamster lung, and also in vitro with acid treatments. Amosite appeared also to fragment but lose more silicon than magnesium ions, at a much slower rate than that of chrysotile, presumably from the difference in their basic structures.

In plain English

This was an animal experiment combined with laboratory tests. The authors placed one 1 mg dose of UICC Canadian chrysotile or amosite asbestos into the windpipes of Syrian golden hamsters. They examined lung fibers at 4 weeks, 56 weeks and 2 years (chrysotile) and 2 years (amosite). Controls sat in water or saline for a week (some also digested in sodium hypochlorite); some control and lung fibers were then acid-treated. Short chrysotile fibers (under 5 micrometres) fell from 38% in controls to 13% at 56 weeks, then made up 57% at 2 years. Chrysotile fibers also became much thinner. Short amosite fibers fell from 41% to 4% at 2 years. After 2 years, 33% of chrysotile and 68% of amosite fibers were asbestos bodies. Chrysotile from the lungs had a significantly higher silicon-to-magnesium ratio than control fibers, and a higher ratio than same-sized control fibers. The authors concluded that chrysotile became progressively shorter and thinner in the lung, mainly by losing magnesium, while amosite changed much more slowly. They stated that their hamster results cannot be applied directly to humans.

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: Animal experiment (single intratracheal instillation in hamsters) combined with in vitro treatment of fibers, analysed by scanning electron microscopy and x-ray energy-dispersive spectrometry
• Who was studied: Syrian golden hamsters, killed at 4 weeks, 56 weeks and 2 years after chrysotile and 2 years after amosite. Lung portions from two to three animals were pooled per group. The total number of animals is not stated.
• Exposure: One intratracheal dose of 1 mg UICC Canadian chrysotile or UICC amosite asbestos in 0.1 ml normal saline. Control fibers were kept for 1 week in distilled water or normal saline with daily agitation, and one saline portion was also digested in sodium hypochlorite. Fibers from some control and lung groups were then treated in vitro with hydrochloric and nitric acid.
• Main results:
  • Chrysotile: short fibers (under 5 micrometres) fell from 38% (control) to 23% at 4 weeks and 13% at 56 weeks after instillation
  • Chrysotile: after 2 years, short fibers predominated at 57% (the abstract gives 56%)
  • Amosite: short fibers were 41% in the control group and 4% 2 years after instillation; 74% of amosite fibers were longer than 10 micrometres at 2 years
  • Chrysotile: the share of naked fibers thinner than 0.05 micrometres rose from 10% to 56% at 4 weeks, and was 95% at 56 weeks
  • Chrysotile: 2 years after instillation, 33% of fibers had formed asbestos bodies, half of them complete; at 56 weeks the figure was 3%
  • Amosite: 2 years after instillation, 68% of amosite fibers were asbestos bodies, almost 70% of them complete
  • Chrysotile: the silicon-to-magnesium ratio in all groups recovered from hamster lungs (overall means 1.456, 1.449, 1.436) was significantly higher than in control groups (1.378, 1.378, 1.354), p less than 0.01
  • Chrysotile: lung-recovered and acid-treated fibers had higher silicon-to-magnesium ratios than control fibers of the same size. Table 1 means for lung groups were 1.498, 1.488 and 1.463 (thinner fibers) and 1.357, 1.353 and 1.369 (0.2 to 0.6 micrometres). Control means were 1.415, 1.414 and 1.390 (thinner) and 1.287, 1.289 and 1.263 (0.2 to 0.6 micrometres).
  • Chrysotile: in all groups, thicker fibers (0.2 to 0.6 micrometres) had a significantly lower silicon-to-magnesium ratio than thinner fibers; the authors reported that this relationship was reversed in amosite
  • Amosite: the silicon-to-magnesium ratio of fibers from the hamster lung was significantly lower than control; after acid treatment the difference between the 2-year and control groups became insignificant
  • Chrysotile asbestos bodies (42 examined at the same spot before and after acid treatment): the silicon-to-magnesium ratio rose significantly after acid (mean 1.615 before, 2.764 after), with marked loss of iron peaks
• The authors' conclusion: The authors concluded that long chrysotile fibers were retained in the lung at first and then became progressively shorter and thinner, mainly by losing magnesium. They concluded that amosite probably lost silicon more than magnesium, and did so much more slowly. They also concluded that long, thick fibers appeared to form asbestos bodies more readily.
• Limitations the authors state:
  • The results cannot be applied directly to humans, because the tendency to form asbestos bodies differs between animal species
  • The amount of asbestos and the way it was introduced differed from normal breathing
  • The amosite given to the hamsters contained more thick fibers than the chrysotile did
  • The absolute number of fibers in the lungs was not measured

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Amosite, Scanning Electron Microscopy (SEM), Asbestos Bodies.

Related studies

• Studies on the inhalation toxicology of two fiberglasses and amosite asbestos in the Syrian golden hamster. Part II. Results of chronic exposure — E.E. McConnell, C. Axten, et al. (1999)
• Studies on the inhalation toxicology of two fiberglasses and amosite asbestos in the syrian golden hamster. Part I. Results of a subchronic study and dose selection for a chronic study — T.W. Hesterberg, C. Axten, et al. (1999)
• Chronic effects of dietary exposure to amosite and chrysotile asbestos in Syrian golden hamsters — E.E. McConnell, A.M. Shefner, et al. (1983)
• Chronic inhalation study of fiber glass and amosite asbestos in hamsters: twelve-month preliminary results — T.W. Hesterberg, C. Axten, et al. (1997)
• Lung proliferative and clearance responses to inhaled para-aramid RFP in exposed hamsters and rats: comparisons with chrysotile asbestos fibers — D.B. Warheit, S.I. Snajdr, et al. (1997)
• Amosite, chrysotile and crocidolite asbestos are mutagenic in Chinese hamster lung cells — S.L. Huang (1979)

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