Coalinga fibre: A short, amphibole-free chrysotile Part 3: Lack of biopersistence

We previously demonstrated, on the basis of detailed morphological and morphometric investigations of a lifetime inhalation study of F344 rats exposed to three sizes of chrysotile fibre, that a short, amphibole-free chrysotile from Coalinga, California failed to induce pathological effects whilst the other two, both long fibres from Canada, were both fibrogenic and tumourigenic. Here, we demonstrate that, as one would predict from their size differences, the Coalinga fibre was almost totally cleared whilst the Canadian fibres were largely retained 1 year post exposure. We therefore propose on the basis of these observations that the observed absence of biological effects noted with Coalinga is potentially attributable to its lack of biopersistence.