then summarizes and compares the cohorts with respect to their informativeness on several issues. It then discusses both the approach and results of statistical analyses, primarily the NCI combined analyses. Analyses reported by investigators for individual studies are not discussed unless they provide insights that are not available from the combined analyses. Discussion of the statistical analysis begins with an overview, which is followed by sections on specific topics. It concludes with an overall evaluation of the analyses and risk models developed in the NCI report. Analyses conducted specifically for the BEIR VI report are described in chapter 3 and appendix A, and are not discussed here. Appendix E provides a comprehensive description of the method for exposure estimation in each study.
The basic features of each of the 11 cohorts included in the NCI analyses are summarized in the text and tables of this section. The statistics presented in Tables D-1 through D-11 refer to the data used in analyses to develop the risk models for this report, which, for 7 of the cohorts, are very similar to data used in the NCI analyses, although in some cases changes in the approach used to allocate person-years resulted in minor changes from tables presented in the NCI report. For Czechoslovakia, exposures were re-evaluated and follow-up data were improved (Tomásek and Darby 1995) in the data set used for the BEIR VI analyses. Some modifications of the data were also made for China, Newfoundland, and France.
Tables D-1 through D-18 present brief descriptions of tabular information on the cohorts. For additional details on these cohorts, the reader is referred to Lubin and others (1994a) and to papers describing results from the individual studies. The cohorts are presented in descending order of number of lung-cancer deaths. In Tables D-1 through D-11, mean values are computed with person-years as weights.
Tin mining in the Yunnan Province in southern China dates back almost 2000 years. The China cohort consists of about 17,000 employees of the Yunnan Tin Corporation (YTC), a large nonferrous-metals industry. YTC, which was formed in 1883 and nationalized in 1949, is the largest employer in Geiju City. The NCI became involved with the health-research unit of YTC and the Cancer Institute of the Chinese Academy of Medical Sciences in the study of the China cohort in 1985. The cohort has the largest number of lung-cancer deaths. Miners were exposed to a range of exposure rates, and exposure was relatively long, being second only to the study of Swedish miners. This is the only cohort with substantial numbers of workers exposed as children, and 735 of 980 lung-cancers occurred in miners first exposed under age 20.