Occupational Health Program, School of Public Health, Seoul National University, Industrial Health Research Institute, Korea.
ABSTRACT
Benzidine Industry in Korea has started after Japan has banned its production in early 1970's. and it has been in operation in Korea for over 20 years. However, it is not known yet whether any bladder cancer has developed from benzidine exposure. This study was done to screen benzidine-exposed workers for bladder cancer, and to examine the feasibility of employing screening test at the workplace. All the workplaces that manufacture or use benzidine for more than 20 years in Korea have been covered in this study, and they include 2 benzidine manufacturing factories, 5 benzidine using factories, as well as 2 benzidine free factories as an outside control. In total, 516 workers were screened with urine stick test and urine cytology test for the evidence of hematuria and abnormal urothelial cells. Each worker was also asked about risk factors and symptoms of bladder cancer including past medical history, smoking, medication and occupational history. Benzidine in the air was measured by personal and area sampling. Out of 516 screened workers, 84(16.3%)workers showed positive hematuria in urine stick test, and 7(1.4%)workers showed degenerative cells in urine cytology tests. Those workers with abnormal urine test results who have been exposed to benzidine for more than 10 years were further screened, and, in total. 23 workers were examined with intra-venous pyelography and cystoscopy. None of those screened had any evidence of bladder cancer. When workers with only past hematuria history were included in the positive hematuria group, 96(18.5%) had positive hematuria. On the multiple logistic regression analysis, positive hematuria was significantly associated with benzidine exposure history of other occupations with elevated bladder cancer risk, pyuria and glycosuria. The association got stronger as direct benzidine exposure was accounted through individual task analysis, and as exposure duration was accounted with tenure analysis. For those with benzidine exposure with more than 10 years of tenure, the odds of having positive hematuria was elevated 2.14(95%C.I is 1.08 to 4.25) times more than for those without exposure. Even though bladder cancer was not detected for several limitations including short observation period, majority of studied workers with short latency, healthy worker effect, and low sensitivity of single screening test in a cross-sectional study, the study results suggest that hematuria screening is a feasible and very useful test for bladder cancer screening among benzidine exposed workers.
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