Environmental Health Perspectives 105, Supplement 5, September 1997: Article by Muhler and Bellmann

Environmental Health Perspectives 105, Supplement 5, September 1997

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Significance of the Biodurability of Man-made Vitreous Fibers to Risk Assessment

Hartwig Muhle and Bernd Bellmann

Fraunhofer-Institut für Toxikologie und Aerosolforschung, Hannover, Germany

Abstract
It is generally agreed that the biodurability of man-made vitreous fibers is a major factor for the characterization of potential health effects. As there is currently no standardization of experimental protocols to determine biodurability, the results of the clearance assays have not been used up to now for regulatory purposes. Methods used to analyze biodurability in animal models are short-term inhalational exposure and intratracheal instillation of rat respirable fibers. Both test methods have strengths and limitations for regulatory purposes. We outline recommended procedures for standardized biodurability assays that can be used to compare different fiber types. In animal experiments, biodurability is difficult to separate from biopersistence, as mucociliary and macrophage-mediated clearance occur simultaneously with dissolution and disintegration. For intratracheal instillation, a sized rat respirable sample must be used. Precautions should be taken to prevent aggregation of fibers in the lungs. Although from a scientific point of view questions remain about quantifying the influence of fiber length, diameter, dose, and exposure route, consistent data on the biodurability of vitreous glass fibers are available which may be used for regulatory purposes. -- Environ Health Perspect 105(Suppl 5):1045-1047 (1997)

Key words : biodurability, mineral fibers, lung, rat, risk assessment

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 in part by the Bundesanstalt für Arbeitsschutz, Dortmund; the German Bundesministerium für Bildung, Forschung und Technologie (BMBF); the Hauptverband der gewerblichen Berufsgenossenschaften; and Rockwool International, Denmark.

Address correspondence to Dr. H. Muhle, Fraunhofer-Institut für Toxikologie und Aerosolforschung, Nikolai-Fuchs-Str. 1, D-30625 Hannover, Germany. Telephone: 49 511 5350 451. Fax: 49 511 5350 155. E-mail: muhle@ita.fhg.de

Abbreviations used: k , clearance rate constant; m, retained fiber mass; MMVF, man-made vitreous fibers; t, time.

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Last Update: October 27, 1997