Re: 'Occupational exposures and risks of liver cancer among Shanghai female textile workers--a case-cohort study'.

摘要

In a recent issue of the journal, Chang et al. reported a protective effect of cumulative exposure to endotoxin or cotton dust on the incidence of liver cancer among female textile workers after allowing for 20 years latency. On the other hand, an unanticipated elevated risk of liver cancer (Hazard ratio = 5.30 with 95% confidence interval: 1.29-21.81, based on three incident cases) was observed among female workers exposed to inks for less than 10 years, but the underlying reasons were not explored by Chang et al.The authors failed to explore the potential confounding effects from hepatitis B virus (HBV) infection and dietary risk factors. This is an intrinsic methodological defect in this type of case-cohort analysis-inadequate exploration of major potential confounding factors for individual outcomes. Controlling for major potential confounding factors is more likely to be possible in a properly conducted nested case-control study. It was possible that workers known to be carriers of hepatitis B or C would be advised against taking up jobs that entailed exposure to endotoxins, and this could adequately explain the apparent protective effects of cotton dust and endotoxin exposures. In any case, exposing workers to endotoxins for their potential protective effect against cancer should not be encouraged, as endotoxins do have their harmful health effects on workers, including byssinosis and other diseases.