To examine in vivo hazards of ingested glass fibers, we administered glass fibers into the diet of Sprague-Dawley rats for 6 months. In the previous studies, it was found that the size of mineral fibers was closely associated with tissue responses We used glass fibers of average dimensions of approximately 2㎛ in diameter and 80㎛ in length. From the results of animal experiments, it was found that there were several types of administration methods to investigate the tissue response caused by glass fibers, including intrapleural, intrathoracic, and intraperitoneal. However, there were no available feeding methods for ingestion. Therefore, we developed a method to make special diet mixed with glass fibers. There were no remarkable changes in growth curve, diet consumption and gross morphology of various organs by ingested glass fibers. Microscopically, inflammation and fibrosis were not observed in gastrointestinal tract until B months of observation period. Scaring electromicroscopic findings and cell proliferative activity revealed by proliferating cell nuclea antigen were not significantly different between glass fiber treated and control rats.
These results suggest that exposure of glass fibers by ingestion can not provoke any tissue reactions including inflammation, fibrosis and neoplastic changes in rats.
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