The 2000 paper by Hodgson and Darnton, HSE statisticians, was welcomed by some but heavily criticised by many respected asbestos scientists. However, this work remains the information source of choice for the HSE, politicians and others. Its good point is that it clearly differentiates the specific risk of mesothelioma between the major asbestos types ranking their relative potency as 1:100:500 for chrysotile, amosite, crocidolite respectively. However, the reasons for giving chrysotile even this level of affect are considered by many to be flawed because of the way in which they assessed certain cohorts and it is noticeable that in a later paper chrysotile is removed from the discussion.
http://annhyg.oxfordjournals.org/content/44/8/565.full.pdf+html
J.T. Hodgson and A Darnton
Ann. occup. Hyg