Environmental Health Perspectives 105, Supplement 5, September 1997: Article by Bellmann et al.

Environmental Health Perspectives 105, Supplement 5, September 1997

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Investigations on Health-related Properties of Two Sepiolite Samples

Bernd Bellmann, Hartwig Muhle, and Heinrich Ernst

Fraunhofer Institute of Toxicology and Aerosol Research, Hannover, Germany

Abstract
Published ip injection studies have shown different biological behavior of different sepiolite samples. There was no evidence for carcinogenic potential of sepiolite from Vicalvaro, Spain, whereas a high tumor incidence was reported for sepiolite from Finland. The low biological activity of the sepiolite from Vicalvaro, compared to the Finnish sample, could be caused by low in vivo persistence or by the short length of the fibers, or both. In this study a further sepiolite sample, obtained as a commercial sample originating from China, was investigated This sample contained a higher fraction of fibers longer than 5 µm, comparable to the Finnish sepiolite sample. The fraction of fibers with a length >5 µm was 0.12 and 2.2% for the Vicalvaro and Chinese sepiolite, respectively. For the fiber fraction longer than 8 µm, the corresponding values were 0.0045 and 0.82%. The in vivo persistence of the sepiolite samples from China and Vicalvaro was analyzed after intratracheal instillation of 2 mg in female Wistar rats. Fiber retention in the lungs was analyzed by transmission electron microscopy at different sacrifice dates up to 12 months after application. For the Vicalvaro sepiolite, a splitting of fiber bundles was found during retention time in the lung. Therefore, no half-time of the fiber clearance could be calculated from the number of fibers. The decrease of the calculated retained fiber mass was faster for the Vicalvaro sepiolite (T _1/2 =89 days) compared to the Chinese sepiolite (T _1/2 =129 days). For 2 or 3 rats per group, at sacrifice date 12 months after ip injection, the lung was investigated by histopathology. The main difference between both treatment groups was a more pronounced fibrotic response in the Chinese sepiolite-treated rats compared to those treated with Vicalvaro sepiolite. It is concluded that both the higher fraction of long sepiolite fibers and the slower elimination rate of the fiber mass in the Chinese sample were important factors for the different biological reaction in comparison with Vicalvaro sepiolite. -- Environ Health Perspect 105(Suppl 5):1049-1052 (1997)

Key words : biodurability, sepiolite, lung, rat, fiber length, histopathology

This paper is based on a presentation at The Sixth International Meeting on the Toxicology of Natural and Man-Made Fibrous and Non-Fibrous Particles held 15-18 September 1996 in Lake Placid, New York. Manuscript received at EHP 26 March 1997; accepted 3 July 1997.

This study was supported by Tolsa, S.A., Madrid, Spain.

Address correspondence to: Dr. B. Bellmann, Fraunhofer-Institut für Toxikologie und Aerosolforschung Nikolai-Fuchs-Str. 1, D-30625 Hannover, Germany. Telephone: 49 511 5350 452. Fax: 49 511 5350 155. E-mail: bellmann@ita.fhg.de

Abbreviations used: D, diameter; L, length; TEM, transmission electron microscopy; WHO, World Health Organization.

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Last Update: October 16, 1997