Case studies in occupational epidemiology. Steenland K, ed. New York: Oxford University Press, 1993 Jan; :170-177
An investigation was performed to evaluate the feasibility of a study of bladder cancer incidence or mortality at a small chemical facility in southern Michigan where workers were subject to exposure to 4,4'-methylenebis(2-chloroaniline) (101144) (MBOCA). This study was described as part of a text book and took the reader through the same steps that the investigator took when conducting the actual study to allow the student to solve the same problems that the investigator solved in the course of the study. Surveys of urinary MBOCA levels after the MBOCA production process had been shut down in 1979 suggested that MBOCA exposures had been substantial. Surfaces throughout the facility were found to be contaminated with MBOCA. Personnel records allowed identification of 552 workers, mostly young white males. A bladder cancer incidence study was undertaken and a screening program was also considered. Both urinalysis and urine cytology were conducted. Of the 5,552 workers identified, 452 participated in a telephone interview, and 385 participated in the urine screening examination. No bladder tumors were reported in the telephone interviews. Approximately 1 year later the first bladder tumor diagnosis was made among the cohorts in this study. His urine cytology had been negative, as was the dip stick test for heme in the urine. However, his blood cell count on the urinary cytology slide had been slightly elevated. He had worked 1 year at the site 8 years prior to diagnosis. Two additional cases were identified as well. While the study results were not definitive, they increase concern about the ability to MBOCA to cause bladder tumors in humans, particularly when combined with animal evidence and the strong chemical structure relationship between MBOCA and other human bladder carcinogens.