Automobile industry occupations and bladder cancer: a population-based case-control study in southeastern Michigan, USA

Objectives: To determine whether employees in the automobile industry in Michigan are at elevated risk of urinary bladder cancer. Methods: The authors conducted a population-based case-control study including 418 cases and 571 controls. History of employment within the automobile industry was coded according to the US Census Bureau Index of Occupations. Logistic regression analyses were adjusted for age at interview, cigarette smoking status, and highest education level, and used to assess associations between bladder cancer and (1) ever working in particular occupations within the automobile industry; and (2) usual occupation — defined as occupation of longest duration for each subject. Results: Ever having worked in the automobile industry and usual employment within the industry exhibited elevated non-significant risks for bladder cancer among assembly line workers, painters and foremen. A higher risk was seen for those who worked for 20 or more years on the assembly line (OR  =  2.10, 95% CI 1.15 to 3.80). Statistical interaction between usual employment on the assembly line and smoking status (>5 pack-years) was demonstrated (OR  =  6.19, 95% CI 2.69 to 14.24). Conclusions: Among workers on the assembly line for at least 20 years, we observed an approximately twofold risk for bladder cancer. Heavy smokers working on the assembly line experience a sixfold risk for bladder cancer. Further research is necessary to verify this finding, identify the exposures that might be contributing to bladder cancer on the assembly line, and examine whether those exposures continue to persist in today’s workplace.