Development of an animal model, techniques, and an exposure system to study the effects of asbestos cement dust inhalation

Our plain-English summary of Development of an animal model, techniques, and an exposure system to study the effects of asbestos cement dust inhalation, by A.P. Wehner, G.E. Dagle, W.C. Cannon (Environmental Research, 1978).

The study

• Authors: A.P. Wehner, G.E. Dagle, W.C. Cannon
• Journal: Environmental Research
• Published: 1978;16(1-3):393-407
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

An aerosol exposure system and procedures for delivering asbestos cement (AC) dust to the lungs of hamsters are described. Groups of hamsters were exposed to AC aerosol concentrations of 1 and 10 µg/liter, respectively, 3 hr/day. 5 days/week, for 3 and 6 months and were sacrificed for histopathologic examination. One subgroup from both the 1- and the 10-µg/liter exposure group was withdrawn from exposure after 3 months and sacrificed after a 3-month recovery period to determine whether or not some of the histologic changes might be reversible. There was an apparent dose-response relationship between AC exposure and the number of asbestos bodies and small randomly distributed foci of alveolar macrophages. No other treatment-related lesions were observed. The 3-month recovery period had no apparent effect.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

In this animal experiment, the authors described a system for exposing hamsters to asbestos cement dust and reported the lung changes seen after up to 6 months. Three hundred 20-week-old male hamsters were divided into a higher-exposure group, a lower-exposure group and an unexposed control group. The dust came from cutting uncoated asbestos cement sheets at an Eternit plant in Belgium and was listed as 11.1% chrysotile by weight. Animals breathed the dust 3 hours a day, 5 days a week, for 3 or 6 months. Measured respirable dust averaged 9.76 micrograms per liter in the higher group and 0.94 in the lower group. Some animals were exposed for 3 months and then observed for 3 more. The only lesions clearly related to exposure were asbestos bodies in very small to small clusters of alveolar macrophages, which are lung scavenger cells. These appeared more common at the higher dose and appeared more pronounced after 6 months than after 3. The 3-month recovery period had no apparent effect. The authors concluded that the hamster was a suitable model for this research. They also noted that higher concentrations, or longer exposure or observation, might have produced different or more pronounced lesions.

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 inhalation experiment in hamsters, with exposure 3 hours a day, 5 days a week (higher, lower and unexposed control groups)
• Who was studied: 300 male Syrian golden hamsters, 20 weeks old, randomly divided into three groups of 100 (two exposed groups and one unexposed control group)
• Exposure: Asbestos cement dust collected from cutting uncoated asbestos cement sheets at the Eternit plant in Kapelle-op-den-Bos, Belgium, and supplied by the company. Table 1 lists the dust as chrysotile 11.1%, Portland cement 53.4% and sand (alpha quartz) 35.6% by weight. Target concentrations were about 10 and about 1 micrograms per liter, for 3 or 6 months.
• Main results:
  • Group 1 (higher exposure) had a mean total dust concentration of 16.25 micrograms per liter, of which 9.76 was respirable. Group 2 (lower exposure) had 1.36 total, of which 0.94 was respirable.
  • Mean fiber counts (fibers longer than 5 micrometers and thinner than 3 micrometers) were 151 per cubic centimeter at the higher level and 15 at the lower level.
  • After either 3 or 6 months of exposure, the only lesions clearly related to the dust were asbestos bodies found in very small to small, randomly distributed clusters of alveolar macrophages.
  • The authors reported an apparent dose-response effect: asbestos bodies and macrophages were more numerous in the higher-exposure animals than in the lower-exposure animals.
  • The changes appeared more pronounced after 6 months of exposure than after 3 months.
  • Animals withdrawn from exposure after 3 months and observed for 3 more months showed no apparent reversal of the changes.
  • Alveolar bronchiolization was more frequent and somewhat more severe in the higher-dose animals examined after 6 months than in controls.
  • Minimal fibrosis was occasionally seen in exposed hamsters at 6 months, but it was not necessarily related to the asbestos bodies and macrophages. Areas of interstitial pneumonitis were present in both control and exposed hamsters.
  • Apart from a small amount of histiocytosis in one mediastinal lymph node, no lesions outside the lung could be related to the dust.
  • Body weight differences between the lower-exposure group and controls at some weighing points were judged neither consistent nor treatment related.
• The authors' conclusion: The authors concluded that the study showed the hamster was suitable as an animal model for studying the effects of inhaled asbestos cement under well-defined experimental conditions.
• Limitations the authors state:
  • The amount of dust deposited in the lungs could not be measured. Atomic absorption spectrophotometry was not suitable, so deposition was only roughly estimated, without allowing for clearance.
  • The authors noted that substantially higher dust concentrations, or longer exposure or observation times, might have produced different or more pronounced lesions.
  • The particle size distribution of the lower-level dust was not determined.
  • Mediastinal lymph nodes were examined in a semirandom manner because they were small and often not present in routine sections.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Dose-response relationship, Asbestos Bodies, Alveolar Macrophage.

Related studies

• The effects of asbestos-cement dust inhalation on baboons — B. Goldstein, I. Webster, et al. (1978)
• Characterization of the lower respiratory tract inflammation of nonsmoking individuals with interstitial lung disease associated with chronic inhalation of inorganic dusts — W.N. Rom, P.B. Bitterman, et al. (1987)
• Accumulation of mixed mineral dusts in the lungs of rats during chronic inhalation exposure — C.H. McMillan, A.D. Jones, et al. (1989)
• Inspection of deteriorating asbestos cement force mains with georadar technique — S. Smolders, L. Verhoest, et al. (2009)
• Natural mineral fibers: conducting inhalation toxicology studies-part B: development of a nose-only exposure system for repeat-exposure in vivo study of Libby amphibole aerosol — A. Wang, A. Gupta, et al. (2023)
• The use of wild animal models to detect evidence of environmental contamination by asbestos-like substance — R. Puleio, M.R. Schiavo, et al. (2013)

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