Animal experiments with chemically treated fibres

After intraperitoneal injection of 25 mg HCI-leached chrysotile into rats acute loxic rats acute toxic effects were observed. Protein might dissolve the amorphous silicic acid ot the leached fibres: this also prevents the tumour induction by doses which are not acutely toxic. The carcinogenicity of very resistant glass fibres was not influenced by HCI and NaOH. The carcinogenic effect of another specimen was strongly reduced by HCI: this treatment did not change the shape of the glass fibres: however, the durability in the lung decreased. 0.3 mg actionolite induced tumours in the abdominal cavity in 83% of the intraperitoneally injected rats. The carcinogenicity decreased to 7% when actionolite was injected in a solution of polyvinylpyridine-N-oxide (PVNO). Application of PVNO separately from chrysotile or actinolite had no significant effect.