Objectives. Transitional cell carcinoma of the urinary bladder is associated with occupational exposure to 4,4'-methylenebis(2-chloroaniline) (MBOCA). A program to monitor MBOCA levels in the work environment and to screen for bladder cancer was performed at four MBOCA manufacturing factories. Methods. The U.S. Occupational Safety and Health Administration analytic method No. 24 was adopted in this study to measure air MBOCA concentrations. A total of 70 MBOCA-exposed workers and another 92 nonexposed workers were recruited for screening. Urine occult blood tests, urine cytology, tests for the urine tumor marker nuclear matrix protein, and abdominal ultrasonography were performed in all patients. Intravenous urography and cystoscopy were used to confirm the presence of bladder cancer. Results. The air concentration of MBOCA was greatest in the purification area (0.23 to 0.41 mg/m(3)), followed by the washing area (less than 0.02 to 0.08 mg/m(3)) and neutralization area (less than 0.05 to 0.06 mg/m(3)). This study identified a current worker with proved bladder cancer. In addition, we also identified 1 worker with suspected malignant cells on urine cytology and 1 worker with atypical cytology combined with gross hematuria. Although the prevalence of atypical urinary cells and the nuclear matrix protein 22 tumor marker was not significantly different between the MBOCA-exposed workers and nonexposed workers as a whole or when grouped by sex, the prevalence of positive occult blood was marginally significantly (P 0.055) greater in male exposed workers (18%) than in male nonexposed workers (7%). Conclusions. The findings of this study support the conclusions from other studies that MBOCA is potentially carcinogenic to humans. Control measures are needed to prevent overexposure from inhalation and skin absorption.
