The Biopersistence and Pathogenicity of Man-made Vitreous Fibers

A summary is given of the pathology results after long-term tests (inhalation and injection into the abdominal cavity) in rats of a Man-made Vitreous Fiber (HT) representing the new biosoluble types. The biosoluble fiber type, HT, is characterized by a relatively high content of aluminium and a relatively low content of silica compared to the traditional stone wool (MMVF21).

HT has a high in-vitro dissolution rate at pH 4.5 and a relatively low dissolution rate at pH 7.4. In a short-term inhalation study the HT fiber was considerably less biopersistent/more biosoluble than MMVF21 and other MMVFs. In accordance with the high biosolubility of HT in long-term inhalation studies MMVF21 caused pulmonary fibrosis, but the HT fiber did not. For both fiber types the incidence of tumors was comparable to the control groups. Also in injection studies the importance of the high biosolubility of HT was confirmed, because MMVF21 caused a significant increase of mesotheliomas in the abdominal cavity while the HT fiber exposed rats did not show any mesotheliomas.

Due to the results from biopersistence and long-term studies the HT fiber type is exonerated from any carcinogen classification by EU and German regulation. The introduction of the HT fiber type has increased the safety margins in manufacturing and use of Man-made Vitreous Fibers.