As far as Health risk is concerned, why is chrysotile so different from amphibole?

There is growing scientific evidence demonstrating that asbestos induced lung cancer, such as asbestosis, is a threshold phenomenon. Low exposures to chrysotile do not present a detectable risk to health. Since total dose over time determines the likelihood of the occurrence and progression of disease, studies suggest that the risk of an adverse outcome may be low, even if high exposures are experienced for a short duration.