This directive was derived based upon an extensive program evaluating current scientific knowledge on fiber pathogenicity and its relationship to the biopersistence of long fibers. Within this context, the biopersistence of fibers longer than 20 µm was found to be a good predictor of the lung burden and early pathological changes in chronic inhalation studies with fibers as well as the tumor response in chronic intraperitoneal studies with fibers. These results were presented in a preliminary form in an internal report to the European Chemicals Bureau (1997b; ECB/TM/15(97)).

This article summarizes the report and expands the analysis that provided the scientific basis for the relationship of biopersistence to the chronic inhalation results.