Objectives To assess the relationship between occupational exposure to metalworking fluids (MWFs) in the steel-producing industry and bladder cancer incidence.
Methods A nested case–control study on bladder cancer was set up in a cohort of workers from six French steel-producing factories. Three controls were randomly selected for each incident bladder cancer case diagnosed from 2006 to 2012. Controls were matched to cases on age at diagnosis and counter-matched on a surrogate measure of exposure to MWFs derived from a job-exposure matrix. Cases (n=84) and controls (n=251) were face-to-face interviewed. Experts assessed occupational exposure to MWFs (straight, soluble and synthetic) using questionnaires and reports from factory visits. Occupational exposures were based on three metrics: duration, frequency-weighted duration and cumulative exposure index. Conditional multiple logistic regressions were used to determine ORs and 95% CIs, taking non-occupational and occupational exposure into account.
Results In the 25 years before diagnosis, ORs increased significantly with duration of exposure to straight MWFs (OR=1.13 (1.02–1.25)) and increased with frequency-weighted duration of exposure to straight MWFs (OR=1.44 (0.97–2.14)). These results remained valid after adjusting for duration of smoking, average number of cigarettes smoked per day, time since smoking cessation and exposure to polycyclic aromatic hydrocarbons (PAHs). ORs also increased with soluble MWFs but not significantly. No significant association was found with older exposures to MWFs or with exposure to synthetic MWFs.
Conclusion The increased risk of bladder cancer observed among workers exposed to straight MWFs and to a lesser extent to soluble MWFs may be explained by the presence of carcinogens (such as PAH) in mineral oils component of straight and soluble oils. Prevention therefore remains necessary in sectors using MWFs.
- bladder cancer
- metalworking fluids
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Contributors Each author has contributed to the submitted work as follows: RC and EB drafted the manuscript and participated to the data collection. RC managed the data. RC and EB performed statistical analyses. EB reviewed the literature and designed the study. All authors participated to the analysis plan. EB developed the job-specific questionnaires. EB managed the exposure assessment. All coauthors collaborated interactively, contributed to the interpretation of the results and discussion and read and approved the final manuscript. Each author believes that the manuscript represents honest work.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Obtained.
Ethics approval ‘Comité Consultatif sur le Traitement de l’Information’ and ‘Commission Nationale de l’Informatique et des Libertés’.
Provenance and peer review Not commissioned; externally peer reviewed.