Occupational exposure to organic solvents and risk of bladder cancer

Bladder cancer has been linked to several occupations that involve the use of solvents, including those used in the dry-cleaning industry. We evaluated exposure to solvents and risk of bladder cancer in 1182 incident cases and 1408 controls from a population-based study. Exposure to solvents was quantitatively assessed using a job-exposure matrix (CANJEM). Exposure to benzene, toluene and xylene often co-occur. Therefore, we created two additional sets of metrics for combined benzene, toluene and xylene (BTX) exposure: (1) CANJEM-based BTX metrics and (2) hybrid BTX metrics, using an approach that integrates the CANJEM-based BTX metrics together with lifetime occupational histories and exposure-oriented modules that captured within-job, respondent-specific details about tasks and chemicals. Adjusted odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated using logistic regression. Bladder cancer risks were increased among those ever exposed to benzene (OR = 1.63, 95% CI: 1.14–2.32), toluene (OR = 1.60, 95% CI: 1.06–2.43), and xylene (OR = 1.67, 95% CI: 1.13–2.48) individually. We further observed a statistically significant exposure-response relationship for cumulative BTX exposure, with a stronger association using the hybrid BTX metrics (ORQ1vsUnexposed = 1.26, 95% CI: 0.83–1.90; ORQ2vsUnexposed = 1.52, 95% CI: 1.00–2.31; ORQ3vsUnexposed = 1.88, 95% CI: 1.24–2.85; and ORQ4vsUnexposed = 2.23, 95% CI: 1.35–3.69) (p-trend=0.001) than using CANJEM-based metrics (p-trend=0.02). There is limited evidence about the role of exposure to specific organic solvents, alone or in combination on the risk of developing bladder cancer. In this study, workers with increasing exposure to benzene, toluene, and xylene as a group (BTX) had a statistically significant exposure-response relationship with bladder cancer. Future evaluation of the carcinogenicity of BTX and other organic solvents, particularly concurrent exposure, on bladder cancer development is needed.