Cancer occurrence among dyestuff workers exposed to aromatic amines. A long term follow-up study

Although the occupational exposure to some aromatic amines is recognized to cause bladder carcinoma, the long term effect of such exposure on the risk for disease, including other malignant tumors, remains unknown.

A total of 442 dyestuff workers exposed to one or more substances including benzidine (BZ), beta-naphthylamine (beta-N), alpha-naphthylamine (alpha-N), and dianisidine were followed completely until December 1992 (average time since first exposure, 39.4 years). Besides the underlying cause of death, the incidence of urothelial carcinoma was determined by periodic urologic screenings.

Analyses of site-specific cancer mortality revealed a remarkable increased risk for bladder carcinoma for those engaged in BZ manufacture (standardized mortality ratio [SMR] = 63.6), BZ use (SMR = 27.0) and beta N manufacture (SMR = 48.4), but not for those who were exposed to alpha-N. The increased risk of cancer mortality for other organs was not significant for any exposure classes. The crude incidence rate per 1000 person-years of bladder carcinoma was estimated to be 8.7 for those engaged in BZ manufacture, 2.9 in BZ use, 7.7 in beta-N manufacture and 1.0 in beta-N use. Regardless of the class or type of exposure, the adjusted incidence rate of urothelial carcinoma increased with the duration of exposure. The adjusted incidence rate for BZ manufacture remained high (3.8-12.8) during the entire observation period, whereas that for BZ use increased from 0.0 to 4.4 as the time since first exposure increased from less than 10 years to 30+ years.

Occupational exposure to either BZ or beta-N demonstrated an extremely strong and prolonged effect on workers' risk for urothelial carcinoma, particularly for bladder carcinoma, but not for malignant neoplasms of other organs.