There are several important strengths of our study.
This study had a substantially larger base cohort, and hence a larger number of of lung cancer cases, than any previously reported study of textile workers.
Our exposure assessment was also more extensive, detailed and specific than those in previous occupational cohort or population-based studies because we were able to obtain complete work history data that could be linked with a specificallydesigned JEM.
Confounding by cigarette smoking, which is an obvious concern in any occupational study of lung cancer, was an unlikely source of bias because of the low smoking prevalence in the cohort.
Data on smoking habits available from the baseline questionnaire administered on entry into the breast self-examination trial, although possibly incomplete, also enabled control of potential confounding.
We did not have data on some other important lung cancer risk factors in China, such as exposure to passive smoke,cooking practices and radon.
Nonetheless, exposures to these factors were unlikely to be related to occupational exposure types and levels experienced by the cohort, and thus were probably not confounders.
Availability of quantitative data for endotoxin allowed control for
potential confounding of associations with other agents, although none was noted.