Document xzQZKqydVonp61nr4DqB2Ry1y

14256997033 2002-02-26 19:09:21 (GMT), page 31 30 Unfortunately, the quantity of samples is no substitute for quality and the QAMA-McGill researchers acknowledged the poor quality ofthe measurements in otter published assessments the exposure data: "We cannot claim precision or certainty for our estimates, only that the available data-more plentiful in this industry than most others were used to the best ofour ability."(Liddell et al. 1984) Despite the fact that the QAMA-McGill researchers recognized that the MI samples were of no practical value they stated that "No attempt was made to extend work histories beyond 1966 because exposure levels in the period 1967-75 were much lower than in the past, and exposure in a short period before death could not be expected to contribute to risk." (Liddell et al. 1984) However, the QAMA-McGill researchers followed the cohort until 1992 and about one quarter ofthe cohort had significant post-1966 exposures long before they died.(Liddell et al. 1998a) Incredibly, although they had access to the cohort and could have prospectively determined exposure levels form 1966 forward, the QAMA-McGi11 researchers merely projected the previous 18 years of exposure data measurements forward. (Liddell et al. 1998a) The QAMA-McGill researchers try to equate the "quantity" of measurements with "quality." Unfortunately, the quantity of samples is also misleading. In fact, hardly any samples were taken, given the number of mines and mills, job classifications, variability of exposures in the same process within and between mines and the eighty-year follow-up period. The QAMA (the mine owners performed the sampling) sampled forty-four mines and each mill and mine had at least eight major processes, each of which resulted in variable particle counts and particle/fiber ratios taken over an eighteen-year period. (2001c) (Gibbs and LaChance 1972) Therefore, on average, the QAMA sampled each of the major mine processes less than once every three years for between 5 and thirty minutes. Furthermore, QAMA never monitored two large cohorts of 30