Chronic inhalation of asbestos and cigarette smoke by hamsters

Our plain-English summary of Chronic inhalation of asbestos and cigarette smoke by hamsters, by A.P. Wehner, R.H. Busch, R.J. Olson, et al (Environmental Research, 1975).

The study

• Authors: A.P. Wehner, R.H. Busch, R.J. Olson, D.K. Craig
• Journal: Environmental Research
• Published: 1975;10(3):368-83
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

One hundred and two male Syrian golden hamsters received chronic exposures to a respirable aerosol of Canadian chrysotile asbestos (mean aerosol concentration = 23 µg/l) 7 hours per day, 5 days per week. Half of the animals were also exposed for 10 minutes to cigarette smoke in modified Hamburg II smoking machines, three times per day, 5 days per week, for the duration of their life span. The other half of the animals received sham-smoke exposures. Another group of 102 hamsters served as controls. Half of the controls received smoke exposures, the other half received sham exposures. Asbestos exposure resulted in earlier and more severe lung lesions than in identical groups of concurrent experiments, which had received life span exposures to aerosols of NiO (53 µg/l) and CoO (10 µg/l), or which were treated with diethylnitrosamine (12 × 0.25 mg by s.c. injection). Asbestosis developed in all animals and forced discontinuation of the asbestos exposures after 11 months. Of 12 lung adenomas found in 510 hamsters, ten occurred among the 102 animals of the asbestos-exposed groups, indicating an early neoplastic response. However, perhaps on account of their significantly shorter life span due to asbestosis, the incidence of laryngeal lesions and of malignant tumors was significantly lower in the asbestos + smoke-exposed group than in the control group having received smoke exposures. Neither a carcinogenic effect of asbestos nor a cocarcinogenic effect of cigarette smoke was observed. Cigarette smoke inhalation resulted in significantly lower mean body weights of the smoke-exposed groups.

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

In plain English

This was an experiment in male Syrian golden hamsters. 102 hamsters breathed a dust of Canadian chrysotile asbestos (average 23 micrograms per liter of air) 7 hours a day, 5 days a week. Half also breathed cigarette smoke three times a day; half got sham smoke. Two control groups of 51 got smoke or sham smoke without asbestos. All asbestos-exposed hamsters developed asbestosis. Asbestos exposure stopped after 11 months because of breathing problems and failing health. No asbestos-exposed hamster developed primary lung cancer. Pleural changes in several animals were inflammation and scarring, with no sign of malignancy. Of 12 lung adenomas among 510 hamsters in the wider program, 10 were in asbestos groups. The asbestos-plus-smoke group had significantly fewer laryngeal lesions and malignant tumors than smoke-only controls, which the authors suggested was possibly due to earlier death from asbestosis. The authors observed no cancer-causing effect of asbestos and no cancer-promoting (cocarcinogenic) effect of smoke in this experiment. They concluded this dose was too high for cancer studies, as early deaths from massive asbestosis might reduce or remove the chance for cancers to develop.

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: lifetime inhalation study in hamsters of chrysotile asbestos alone and combined with cigarette smoke. It was part of a larger program that also tested cobalt oxide, nickel oxide and diethylnitrosamine.
• Who was studied: 102 male Syrian golden hamsters, about 2 months old at the start, exposed to asbestos (51 with smoke, 51 with sham smoke), plus 102 control hamsters (51 smoke plus sham dust, 51 sham smoke plus sham dust). The wider program used 510 hamsters in ten groups of 51. Location and dates are not stated in the text.
• Exposure: Respirable aerosol of Canadian chrysotile asbestos (UICC reference samples), mean concentration 23 micrograms per liter, 7 hours per day, 5 days per week. Exposure was stopped after 11 months. Half of the animals were also exposed nose-only to cigarette smoke (University of Kentucky research cigarettes) for about 10 minutes, three times per day, in modified Hamburg II smoking machines.
• Main results:
  • Asbestosis developed in all asbestos-exposed animals, forcing the asbestos exposures to stop after 11 months.
  • Hamsters that died after 7 months of asbestos exposure already showed early asbestosis.
  • Asbestos bodies were found in the lungs of all hamsters in the asbestos-exposed groups.
  • Lining-cell growths in the lungs of asbestos-exposed hamsters stayed benign. No animal developed a primary lung malignancy.
  • Several asbestos-exposed hamsters showed involvement of the pleura, mediastinum and epicardium (mainly chronic inflammation and fibrosis, occasionally some mesothelial reaction), with no suggestion of malignancy.
  • Of 12 lung adenomas found in all 510 hamsters, 10 occurred among the 102 asbestos-exposed animals. The authors interpreted this as an early neoplastic response.
  • Of these lung adenomas, 7 were in the asbestos plus smoke group and 3 in the asbestos plus sham smoke group.
  • Among asbestos-exposed hamsters, laryngeal lesions were more frequent with smoke than with sham smoke (6 vs 2; epithelial lesions of the larynx 4 vs 0), but the difference was not statistically significant.
  • Laryngeal lesions of all types (Table 2, groups of 51): asbestos plus smoke 6 (12%), asbestos plus sham smoke 2 (4%), smoke plus sham dust 25 (49%), sham controls 2 (4%).
  • Laryngeal lesions and malignant tumors were both significantly less common in the asbestos plus smoke group than in the smoke-only control group (laryngeal lesions p less than 0.01; malignant tumors p less than 0.05).
  • The asbestos plus smoke group lived longer than the asbestos plus sham smoke group, but the difference was not significant at the P = 0.05 level.
  • Death in most asbestos-exposed hamsters was attributed to asbestosis.
  • Smoke-exposed groups had significantly lower mean body weights.
• The authors' conclusion: The authors reported that neither a carcinogenic effect of asbestos nor a cocarcinogenic effect of cigarette smoke was observed in this experiment.
• Limitations the authors state:
  • The authors stated that the asbestos concentration of 23 micrograms per liter, given 5 days per week, was too high for carcinogenicity or cocarcinogenicity studies. It caused massive asbestosis and early death, which might reduce or remove the chance for malignant tumors to develop.
  • The authors stated that asbestosis overwhelmed the animals and masked trends seen in the other groups.
  • The authors stated that the body-weight difference between the sham controls and the asbestos plus sham smoke group may not be meaningful, because the sham controls were unusually heavy for hamsters.

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, Asbestos Exposure, Carcinogenic.

Related studies

• Investigations on the effects of chronic cigarette-smoke inhalation in Syrian golden hamsters — W. Dontenwill, H.J. Chevalier, et al. (1973)
• 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 study of fiber glass and amosite asbestos in hamsters: twelve-month preliminary results — T.W. Hesterberg, C. Axten, et al. (1997)
• 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)
• Effects of cigarette smoke exposure on retention of asbestos fibers in various morphologic compartments of the guinea pig lung — A. Churg, V. Tron, et al. (1987)
• Effects of cigarette smoke on the clearance of short asbestos fibres from the lung and a comparison with the clearance of long asbestos fibres — A. Churg, J.L. Wright, et al. (1992)

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