8234966 Occupational exposure to chromium(VI) and five selected cancer sites: systematic review and meta-analyses

<h3>Objective</h3> Hexavalent chromium (Cr(VI)) is a human carcinogen. It is unclear whether Cr(VI) can cause cancer of the small intestine, oral cavity, pancreas, prostate and urinary bladder. We performed a systematic review and meta-analyses of epidemiological studies on occupational exposure to Cr(VI) and incidence and mortality of these cancer sites. <h3>Material and Methods</h3> A comprehensive review of human studies on Cr(VI) and cancer was performed in Embase and Scopus. 131 potentially relevant epidemiological studies were identified. Study quality was assessed using Newcastle-Ottawa Scale. 29 publications including 81 observations for meta-analyses were based on cohort or case-control studies with exposure assessment of sufficient quality. Site-specific random-effects meta-analyses were done separately for incidence and mortality. Sensitivity analyses focused on the studies with the highest quality scores. <h3>Results</h3> No indications for an association between Cr(VI) exposure and oral or small intestine cancer were found. Incidence of pancreatic cancer was not associated with Cr(VI) exposure (meta-RR 1.04; 95%CI 0.85-1.28) while for specific mortality RR was 1.41 (0.96-2.08) with moderate heterogeneity (I2=41%) and an asymmetric funnel plot (Egger’s test; p=0.002). For incidence of prostate cancer meta RR was 1.16 (0.99-1.37) while the RR for mortality was 1.03 (0.84-1.25). For bladder cancer, RR was 1.04 (0.91-1.20) for incidence and 1.76 (1.20-2.60) for mortality. <h3>Conclusion</h3> There are indications that pancreas, prostate and bladder cancer may be related to occupational exposure to Cr(VI) compounds, but in the meta-analyses sufficient evidence was not provided. For oral cavity and small intestine cancer, reported indications from animal models were not supported by human studies.