Document evjN2beQObYYboOMJMEE2rb3m

14256997033 2002-02-26 19:09:21 (GMT), page 45 44 great assurance that the particle/fiber ratio applied in the circumstance under investigation." [Emphasis added](Liddell et al. 1998c) Liddell (1998) again recognized the inadequacy of their dose estimates. "Liddell et al. (1984) estimated a factor to convert dust counts to fibre counts as about 3.5 (fibres/ml), mpcfbut stated this would he quite unreliable except applied to mean dust levels for substantial groups of Quebec asbestos workers. For the many jobs in which the2217 menincluded in their studyhad worked, die fibre:dustratioshad ranged from 03 to 30 (fibres:ml):mpcf virtually independently of the dust level; in the current study ratiosjob byjob must have varied similarly so that the classification ofjobs by dust category would not be a reliable classification by fibre count" [Emphasis added] (Liddell et al. 1998c) They also understood why the dose estimates were so inaccurate. Fiber dust ratios differed by orders ofmagnitude for different types of work. In addition fiber dust ratios differed by orders of magnitude for the same work process at different points in time. "The two important reports by Gibbs and Lachance (1972); Gibbs and Lachance (1974) give some indication ofthe inherent complexity, a simple example is that work on the tailings dump in 196X was extremely dusty but, as most of the fibre would have been extracted the fibre: dust ratio must have been quite low."j|m| The exposure data was so inaccurate that "taken at face value" exposures were protective for the workers. In other words, un-manipulated, the exposure data indicated that chrysotile exposure prevented workers from developing pneumoconiosis, lung cancer or mesothelioma. The QAMA- McGill researchers realized that this result was so extreme the scientific community would not accept it. It would expose the inadequacies of the entire 40-year study program and 44