Asbestos use and carcinogenicity in Germany and a comparison with animal studies

Our plain-English summary of Asbestos use and carcinogenicity in Germany and a comparison with animal studies, by F. Pott (The Annals of Occupational Hygiene, 1994).

The study

• Author: F. Pott
• Journal: The Annals of Occupational Hygiene
• Published: 1994;38(4):589-600, 420
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The centralized structure of economic affairs in the former German Democratic Republic (East Germany) and the isolation from the free market led to the situation that imported asbestos was almost exclusively chrysotile. More than 90% came from the Kiembay mining area in the Ural Mountains, and about 7% was long-fibre chrysotile from Canada. Sturm and co-workers detected 1082 mesothelioma cases from 1960 to 1990 in the counties of Magdeburg and Halle. In 843 of these cases an exposure to asbestos was evident. Seventy-two cases were exposed to chrysotile only. Suspected exposure to amphiboles imported before World War II or to fibre contained in talc could not be substantiated. Up to now, there have been no analyses of lung fibre burdens from such cases. Reviewing the carcinogenicity studies in rats performed by inhalation or intra-cavitary injection of chrysotile, amosite and crocidolite fibres, the results give no clear indication of a lower carcinogenic potency per chrysotile fibre than per amphibole fibre if equal fibre numbers and fibre sizes are applied, although the chrysotile content of the lungs is relatively low. Also the mesothelioma rates after inhalation exposure to extremely high concentrations of the different asbestos fibre types are similar for chrysotile and the amphiboles and in the region of 5%. Compared with the asbestos-related cancer rates in chrysotile textile workers, rats have to be exposed to a more than 100-fold higher fibre concentration than humans to induce the same lung tumour incidence.

In plain English

This 1993 workshop paper on chrysotile was mainly a review, though it included previously unpublished rat data. The author described asbestos use in Germany, presented other researchers' mesothelioma data from two East German counties, and reviewed rat experiments. East Germany imported almost exclusively chrysotile: about 1.41 million tons, 1960 to 1989. Of 1082 mesothelioma cases detected in Magdeburg and Halle from 1960 to 1990, 72 were in workers exposed to chrysotile only. The author wrote that suspected amphibole exposure could not be substantiated in them. A West German lung-fibre case-control study by others found a clear dose-response only with amphiboles; the author questioned lung fibre burden at death as a dose measure. In nine rat inhalation publications, the author counted 297 rats with lung tumours and 13 with pleural mesotheliomas after chrysotile, and 174 and 10 after amphiboles; the mesotheliomas were given as 4.2% and 5.4% of these tumour-bearing rats, not of all exposed rats. The author concluded that the higher mesothelioma effect of crocidolite and amosite seen in humans could not be confirmed in rats, after inhalation or injection.

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: Mainly a review and workshop paper. It covers asbestos import data, mesothelioma register data from other researchers (Sturm et al.), a West German case-control lung-fibre study by others (Rodelsperger et al.), and rat inhalation and injection carcinogenicity studies. It also includes some previously unpublished rat injection results and latency data.
• Who was studied: Mesothelioma cases detected from 1960 to 1990 in the counties of Magdeburg and Halle, East Germany (about 3 million inhabitants), as reported by Sturm et al. Also 47 mesothelioma cases and 63 controls in a West German case-control study, and rats in experimental studies.
• Exposure: Chrysotile, mostly from the Kiembaj mining area in the Ural Mountains, with about 7% long-fibre chrysotile from Canada, used in East German asbestos-cement products. The rat studies used chrysotile, amosite and crocidolite given by inhalation or by intraperitoneal or intrapleural injection.
• Main results:
  • In Magdeburg and Halle, 1082 mesothelioma cases were detected over 30 years. The author estimated that about 120 spontaneous mesotheliomas would be expected in that period.
  • Although almost no amphiboles were imported after 1945, amphibole exposure was evident in 426 of the cases.
  • Seventy-two mesotheliomas occurred in workers exposed to chrysotile only. In these cases, suspected amphibole exposure could not be substantiated.
  • In the West German case-control study (47 mesothelioma cases, 63 controls), lung fibre analysis showed a clear dose-response relationship only with amphibole fibres and not with chrysotile.
  • In inhalation studies, the cancer risk from asbestos in rats was much lower than in humans: about two orders of magnitude lower for lung tumours and about three for mesotheliomas.
  • Across nine rat inhalation publications: in the chrysotile groups, 297 rats had lung tumours and 13 had pleural mesotheliomas. In the amphibole groups, 174 had lung tumours and 10 had pleural mesotheliomas. The percentages given (4.2% for chrysotile, 5.4% for amphiboles) are mesotheliomas as a share of these tumour-bearing rats (lung tumours plus mesotheliomas), not of all exposed rats.
  • In recent inhalation experiments in one laboratory, chrysotile and crocidolite produced similar rat tumour incidences of about 20%, with similar numbers of fibres in the lungs.
  • In intraperitoneal injection studies, only 50 micrograms of UICC Canadian chrysotile induced serosal tumours in about 30% of treated rats. Relative to the number of fibres injected, the chrysotile and crocidolite preparations did not differ significantly in mesothelioma-inducing potency.
  • In an intrapleural injection study in rats, the tumour-per-fibre ratio depended on the fibre dimensions chosen. For long, thin 'Stanton' fibres, chrysotile's potency per fibre was 1 to crocidolite's 68.
• The authors' conclusion: The author concluded that, across the rat carcinogenicity studies, the higher mesothelioma-inducing effect of crocidolite and amosite compared with chrysotile seen in humans could not be confirmed, either after inhalation or after injection. The author also concluded that chrysotile was not less effective than the amphiboles for lung carcinogenicity in rats.
• Limitations the authors state:
  • Clinical data were incomplete for some of the East German mesothelioma cases.
  • The author argued that the total lung fibre burden at the end of life is not a reliable measure of the fibre dose at the target cells decades earlier.
  • The author considered the rat inhalation model too insensitive to show a mesothelioma-inducing effect of relatively short fibres.
  • No reliable data yet existed to replace hypothetical carcinogenicity factors for fibres of different dimensions.
  • The significance of chrysotile fibre bundles splitting, for chrysotile's carcinogenic potency, was not yet clear.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Crocidolite, Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Chrysotile, Mesothelioma, Amphibole Group, Talc, Amosite, Crocidolite, Carcinogenic.

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• Asbestos-related diseases in the Federal Republic of Germany — H.J. Woitowitz, L. Beierl, et al. (1981)
• The carcinogenicity of dietary acrylamide intake: a comparative discussion of epidemiological and experimental animal research — J.G. Hogervorst, B.J. Baars, et al. (2010)
• Use of asbestos, health risks and induced occupational diseases in the former East Germany — W. Sturm, B. Menze, et al. (1994)

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