Extended Mortality Follow-up of a Cohort of Dry Cleaners.

Background: Dry cleaning workers are commonly exposed to tetrachloroethylene, a suspected bladder carcinogen, and other organic solvents. The health risks associated with solvent exposures in this industry are unclear.

Methods: We extended mortality follow-up of 5,369 dry cleaning union members in St. Louis to further investigate solvent-related risks. We added 22 years of follow-up, from 1993 through 2014, via linkage to the National Death Index. Using Cox proportional hazards modeling, we computed hazard ratios (HRs) and 95% confidence intervals (CIs) relating cause-specific mortality with levels of a solvent exposure index previously developed by an industrial hygienist based on workers' job titles from union records. The models were fit adjusting for age, sex, and decade of union enrollment, and assuming different exposure lags.

Results: In internal analyses of estimated solvent exposure with a 20-year lag, we observed exposure-response relationships for bladder cancer (HR medium exposure = 4.2; 95% CI = 0.7, 24.5 and HR high exposure = 9.2; 95% CI = 1.1, 76.7 vs. no exposure; Ptrend = 0.08) and kidney cancer (HR = 4.1; 95% CI = 0.7, 22.5 and 24.4; 2.9, 201.6; Ptrend = 0.004). High exposure was also associated with heart disease (HR = 1.6; 95% CI = 1.1, 2.2) and lymphatic/hematopoietic malignancies (HR = 4.3; 95% CI = 1.4, 13.6).

Conclusions: These findings are, to the best of our knowledge, the first cohort evidence relating solvent exposure levels among dry cleaners to elevated risks of selected cancers and heart disease. Additional studies employing solvent-specific exposure assessment are needed to clarify cancer risks associated with tetrachloroethylene.