Epidemiologic evidence of cancer risk in textile industry workers: a review and update.
A meta-analysis of epidemiologic studies for textile industry workers was undertaken in an attempt to evaluate whether the cancer risk varies within the textile industry in relation to the job held or the textile fiber used. We combined studies published up until 1990, when an ad hoc IARC Monograph was issued, and those published after 1990 with the aim of appreciating evidence of reversing trends in cancer risk. Observed and expected cases reported in the original studies were summed up and the totals were divided to obtain a pooled relative risk (PRR) with a 95% confidence interval (CI) estimated with a fixed-effect model. We calculated a chi-square test (chi2) of heterogeneity among studies. When PRR and chi2 were both significant, PRR and CI were calculated with a random-effect model and the source of heterogeneity was investigated. Lung cancer risk was around 0.4 in the first study on cotton workers published in 1936, around 0.7 in subsequent studies, mostly published in the 1970s and 1980s, and around 1.0 in the last studies published in the 1990s. Papers published in the 1970s and 1980s produced consistent risk estimates for lung cancer risk, which was significantly lower than 1.0 in workers exposed to cotton (PRR = 0.77; CI = 0.69-0.86) and wool dust (0.71; 0.50-0.92), as well as in carders and fiber preparers (0.73; 0.54-0.91), weavers (0.71; 0.56-0.85), and spinners and weavers (0.78; 0.66-0.91). Lung cancer PRRs did not significantly deviate from 1.0 in textile workers using synthetic fibers or silk, and in dyers. Increased PRRs were found for sinonasal cancer in workers exposed to cotton dust, and in workers involved in spinning or weaving (4.14; 1.80-6.49). PRR was 1.46 (1.10-1.82) for cancer of the digestive system in textile workers using synthetic fibers or silk, and 1.34 (1.10-1.59) for colorectal cancer in spinners and weavers. The increased bladder cancer PRR in dyers (1.39; 1.07-1.71) is generally attributed to textile dye exposure. In studies published after 1990, there is a general tendency to move toward unity for all the cancer risk estimates, leading to an increasing heterogeneity among studies. Since adjustment for smoking made little difference to the findings, the latter could be attributed to the exposure to textile dusts. The recent findings could be due to a lowering of dust concentration in the workplaces. The reduction of cases of upper respiratory tract cancer parallels with a corresponding increase of lung cancer cases. So, preventive measures have paradoxically increased the lung cancer burden to the textile workers.