Document MMR8LgVDjyZeQ2bEEmVKMapYa

566 I. T. Hodgson and A. Oarmon I exposure was available either as an average for the Excess lung cancer measure cohort as a whole, or for individual subgroups. Seven Excess overall lung cancer mortality has been teen such cohorts were identified (Albin el at., 1990a: de Klerk er at.. 1994; Dement ft til., 1994: Enterline er at., 1987: Fmkelstein. 1984; Hughes era/.. 1987: Liddell er at.. 1997; McDonald er al.. 1983b. 1984; expressed as a percentage excess of expected lung cancer mortality per unit of cumulative exposure. /?c = m(0L-EL)KEL.X) Neubttget and Kundi. 1990; Newhouse and Sullivan, 1989; Peto er al.. 1985: Piolatto er at.. 1990; Seidman Where 0L and j. are the numbers of observed and er /., 1986; Seidman and SelikotV. 1990; Sluis- expected lung cancers, respectively and X is cohort Cremer er til., 1992; Talcott er a/.. 1989). Three of mean exposure. This estimate of the lung cancer risk the selected cohorts have been split into sub-cohorts is described as the 'cohort average' estimate. 95% which have been separately treated in this review: the confidence limits for the cohort average estimate South African crocidolite and amosite mining cohorts have been calculated assuming a Poisson distribution have been treated separately; the New Orleans asbes for 0,.. tos cement cohort has been split into the two separate plants covered, since the mix of fibres used in the two plants was different: and the Carolina textile cohort has been split by sex, since the results for men and women were rather different. The cohorts have been referred to by their geographical location except for cohorts 3 (Enterline er al., 1987) and 17 (Newhouse Mesothelioma measure Mesothelioma mortality was expressed as a per cent of expected mortality from all causes (adjusted to an age of first exposure of 30) per unit of cumulat ive exposure. uad Sullivatt. 1.989) which arc identified by a com Rm= lOQO^E^pO pany name, and cohort 15 (Albin er al., 1990a) where the name of the principal author on the cohort has been used. Where 0M is the number of mesothelioma deaths, AJj the total expected deaths from all causes adjusted to an age of first exposure of 30, and X the mean Information extracted Information was extracted from the identified reports on the following: cumulative exposure. (See Appendix A for a dis cussion of this measure, and the calculation of EMl). When the expected all causes mortality was not avail able, the denominator was taken to be the total The number of deaths in the cohort from all causes observed deaths less the total of asbestos-related and from lung cancer, and the corresponding deaths (mesothelioma, osbestosis and any excess lung SMRs; cancer deaths). A 95% confidence interval for RM was Dose specific lung cancer SMRs (or rates), calculated assuming a Poisson distribution for 0M. where available; The number of mesothelioma deaths in the cohort (for pleural and peritoneal mesothelioma Treatment of `best evidence ' cause of death data separately); In some studies causes of death have been assigned The rates of mesothelioma by categories of time in two ways, one based purely on data given on the since first exposure; The process/type of work being carried out; death certificates (DC), the other using other data (e.g. -- autopsy reports) to establish a 'best evidence' (BE) Cohort recruitment period and duration of follow cause of death. For lung cancer this review has gener up; ally used the DC data, since this preserves compar Average age at first exposure, when available; ability with the reference rates, and with the majority The type(s) of asbestos fibre used in the process; of other studies. For mesothelioma however, the BE The average fibre levels for the entire cohort and data has been used, since reference rates are inappro the average employment duration for workers in priate, and most studies use some sort of best evi the cohort, or simply the average cumulative dence judgement to identify mesotheliomas. exposure for the entire cohort; It might be thought that where reference rates ore Information about the smoking habits of the workera in the cohort where available; derived from DC data (as in the SMR analyses in this report) the observed deaths on a DC basis should always be used. The argument is not os clear cut as The sex of the workers. it seems. The coding of death certificates is subject to a range of errors, and the net error in the count of Some general issues on the summaiy of outcome deaths coded to lung cancer on national death certifi and exposure measures are discussed below. A more cates will be determined by the balance of these errors detailed discussion on some of these points is given across the whole population. One of these errors is in Appendix A, and the extracted data is shown in the tendency of pleural mesothelioma deaths to be full in Tables 12 and 13. coded to lung cancer. In the population as a whole. 11 ...... vjfrr.rs: