Asbestos cement dust inhalation by hamsters

Our plain-English summary of Asbestos cement dust inhalation by hamsters, by A.P. Wehner, G.E. Dagle, W.C. Cannon, et al (Environmental Research, 1978).

The study

• Authors: A.P. Wehner, G.E. Dagle, W.C. Cannon, R.L. Buschbom
• Journal: Environmental Research
• Published: 1978;17(3):367-89
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

Abstract

Two groups of 96 male Syrian golden hamsters were exposed to respirable asbestos cement aerosol at concentrations of approximately 1 and approximately 10 micrograms/liter, respectively, 3 hours/day, 5 days/week. Average fiber counts ranged from 5 to about 120 fibers/cm3. Each group was randomly divided into six subgroups of 16 animals. The first subgroup was sacrificed after 3 months of exposure, the second after 6 months, and the third after 15 months. The fourth subgroup was withdrawn from exposure after 3 months, observed for an additional 3 months, and then sacrificed. The fifth and sixth subgroups were withdrawn after 3 and 6 months of exposure, respectively, and maintained for observation up to the 15-month exposure point of the third subgroup at which time all surviving animals were sacrificed. All other experimental procedures were similar to those delineated in a previous publication describing the development of an animal model, techniques, and an exposure system for asbestos cement dust inhalation (A. P. Wehner, G. E. Dagle, and W. C. Cannon, 1978, Environ. Res. 16, 393-407). The asbestos cement exposures had no significant effect on body weight and mortality of the animals. Higher aerosol concentration and longer exposure times increased the number of macrophages and ferruginous bodies found in the lungs of the exposed animals. Recovery periods had no effect on the incidence of macrophages and ferruginous bodies. The incidence of very slight to slight fibrosis in the animals sacrificed after 15 months of exposure shows a significant (P less than 0.01) trend when the untreated control group and the 1 and 10 microgram/liter dose level groups are compared, indicating a dose-response relationship. Development of minimal fibrosis continued in animals withdrawn from exposure. No primary carcinomas of the lung and respiratory tract and no mesotheliomas were found.

In plain English

In this animal experiment under a contract with Eternit, which supplied the dust, two groups of 96 male Syrian golden hamsters breathed asbestos cement dust from cut asbestos cement sheets (about 10.5% chrysotile asbestos). They were exposed at about 1 or 10 micrograms per liter of air, 3 hours a day, 5 days a week. A third group of 96 was not exposed. Subgroups were killed after 3, 6 or 15 months, some after being removed from exposure. Exposure had no significant effect on body weight or survival. Higher dust levels and longer exposure increased macrophages and ferruginous bodies in the lungs. After 15 months' exposure, very slight to slight lung fibrosis was seen in 1 of 14 controls (7%), 4 of 16 (25%) at the lower level and 13 of 15 (87%) at the higher level, a statistically significant dose trend. Minimal fibrosis continued to develop after exposure stopped. No primary carcinomas of the lung or respiratory tract and no mesotheliomas were found. The authors described the fibrotic response as only slight at these concentrations.

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: Controlled animal inhalation experiment in hamsters with an untreated control group, serial sacrifices at 3, 6 and 15 months, and subgroups withdrawn from exposure for recovery/observation. The work was conducted under contract with Eternit.
• Who was studied: Male Syrian golden hamsters (outbred LaK:LVG strain): two exposed groups of 96 and one untreated control group of 96, each divided into subgroups of 16. The hamsters were 12 weeks old at the start, and exposures lasted 67 weeks (about 15 months). The study was done at Battelle, Pacific Northwest Laboratories, Richland, Washington.
• Exposure: Asbestos cement dust collected from cutting uncoated asbestos cement sheets at the Eternit plant in Kapelle-op-den-Bos, Belgium. Its approximate composition was cement ~83%, chrysotile asbestos ~10.5%, water ~6% and cellulose ~0.5%. Target concentrations were ~1 and ~10 µg/liter, given 3 hours/day, 5 days/week. Measured total concentrations were 1.7 and 14.6 µg/liter, and respirable concentrations were 1.3 and 9.9 µg/liter. The authors stated this corresponded to 0.1 and 1 µg asbestos per liter, or 1 and 10 times the German TRK for chrysotile. Fiber counts (fibers longer than 5 µm) were 5.0 to 13.0 fibers/cm3 in the low-level aerosol and 30 to 122 fibers/cm3 in the high-level aerosol.
• Main results:
  • The authors judged that body weight differences among the groups were not treatment related.
  • There was no statistically significant difference among the groups in the number of hamsters alive at final sacrifice. Eight hamsters died in the first 6 months; five of these, from the high-dose group, were accidentally soaked by a malfunctioning drinking water nozzle. A further 27 died between the 6-month and 15-month points.
  • Higher aerosol concentration and longer exposure increased the number of macrophages and ferruginous bodies in the lungs of exposed hamsters.
  • Pulmonary fibrosis related to exposure appeared only in the 15-month exposure groups and did not exceed the grade of slight.
  • Incidence of very slight to slight fibrosis among the assessed hamsters after 15 months of exposure: controls 1/14 (7%); 1 µg/liter group 4/16 (25%); 10 µg/liter group 13/15 (87%). The control and high-dose counts are garbled in Table 7 of the OCR. They are taken from the severity counts in Tables 9 and 11: 13 normal and 1 very slight among the 15-month controls, and 2 normal, 6 very slight and 7 slight in the 10 µg/liter 15-month group.
  • The fibrosis incidence after 15 months showed a significant trend (P < 0.01) toward higher incidence and severity with dose level when controls and the 1 and 10 µg/liter groups were compared.
  • Hamsters exposed for 3 months developed fibrosis during the recovery period after exposure stopped, while controls did not.
  • At 6 months, average wet lung weight in the high-dose group was significantly higher than in the low-dose and control groups. At 15 months there was no statistically significant difference in weight data among subgroups.
  • The role of the dust in causing emphysema remained unclear. At 6 months there was more very slight emphysema in the 10 µg/liter group than in controls, but at 15 months there was no significant difference.
  • No primary carcinomas of the lung and respiratory tract and no mesotheliomas were found.
• The authors' conclusion: The authors stated that an interstitial response including alveolar fibrosis was observed in exposed hamsters and that minimal fibrosis continued after withdrawal from exposure. They concluded that the fibrotic response was only slight at the concentrations used, which they said corresponded to 1 and 10 times the German TRK for asbestos. As possible explanations, they suggested the different mode of administration compared with intrathoracic injection studies. They also suggested that processing into asbestos cement might change or coat the fibers, a hypothesis they said might appear less attractive in light of other findings.
• Limitations the authors state:
  • Only one filter was counted at each fiber-count sampling time, so between-filter variation could not be estimated.
  • Fiber counts came from only four short spot samples over the 15 months, so the authors cautioned against giving much weight to variation in the high-level counts.
  • Reduced air flow rates for the last two fiber samples might have caused loss of some larger fibers, contributing to the lower counts.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Macrophage, Ferruginous body, Fibrosis, Dose-response relationship, Carcinoma, Mesothelioma.

Related studies

• Chronic inhalation study of fiber glass and amosite asbestos in hamsters: twelve-month preliminary results — T.W. Hesterberg, C. Axten, et al. (1997)
• Development of an animal model, techniques, and an exposure system to study the effects of asbestos cement dust inhalation — A.P. Wehner, G.E. Dagle, et al. (1978)
• Induction of pulmonary carcinoma in rats by chronic inhalation of dust from pulverized asbestos pipe covering — B.K. Leong, R.J. Kociba, et al. (1978)
• 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 inhalation of asbestos and cigarette smoke by hamsters — A.P. Wehner, R.H. Busch, et al. (1975)
• The pulmonary toxicity of talc and granite dust as estimated from an in vivo hamster bioassay — B.D. Beck, H.A. Feldman, et al. (1987)

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