The in vitro activities of a highly carcinogenic mineral fibre--potassium octatitanate.

The in vitro activities of a highly carcinogenic potassium octatitanate fibre (Fybex) have been investigated. This material caused a low level of in vitro transformation in C3H10T1/2 cells and is thus more active in this assay than the UICC amphibole asbestos samples but less active than fibrous erionite. This ranking is in accord with carcinogenicity in vivo. However Fybex had no detectable activity in an assay for DNA damage based on the S1-nuclease sensitivity of the DNA from exposed cells. In that assay crocidolite asbestos was more active than either of the more carcinogenic dusts. It is suggested that the activities of amphibole asbestos in assays for genetic toxicity may depend on the production of free radicals via a catalytic reaction requiring the presence of transition elements which are either not present or only present at low concentrations in erionite or Fybex. This type of reaction may not be related to in vivo carcinogenicity. The action of fibrous dusts against macrophage-like cells, measured in this instance by the release of arachidonic acid, remains one of the best measures of biological activity.