Contemporary Occupational Carcinogen Exposure and Bladder Cancer: A Systematic Review and Meta-analysis

Importance: Bladder cancer (BC) is a common disease. Despite manufacturing and legislative changes to workplace hygiene, many BCs still arise through occupational carcinogen exposure. Objective: To profile contemporary risks of occupational BC. Data Sources: A systematic review using PubMed, Medline, Embase, and Web of Science was performed in October 2012 (initial review) and May 2014 (final review) and was updated in June 2015. Study Selection: We identified 263 eligible articles. We excluded reports in which BC or occupation were not the main focus, and those with insufficient case, risk, or confidence interval data. We selected the most recent data from populations with multiple reports. Data Extraction and Synthesis: Reports were selected by 2 of us independently. We combined odds ratios and risk ratios (RRs) to provide pooled RRs, using maximally adjusted RRs in a random effects model. Heterogeneity and publication bias were assessed using I2 and Begg and Egger tests. Risk estimates were annotated by occupational class using Nordisk Yrkesklassificering, or Nordic Occupational Classification, and International Standard Classifications of Occupations (NYK and ISCO-1958) Codes. Main Outcomes and Measures: Occupations were profiled by BC incidence and mortality risk over time. After data collection, we detected a sex difference in these profiles and recorded this as a secondary outcome. Results: Meta-analysis revealed increased BC incidence in 42 of 61 occupational classes and increased BC-specific mortality in 16 of 40 occupational classes. Reduced incidence and mortality were seen in 6 of 61 and 2 of 40 classes, respectively. Risk varied with sex and was greatest in men (standardized incidence ratio, 1.03 [95% CI, 1.02-1.03]; P < .001]). From the 1960s to the 1980s, there was a steady decline in standarized incidence ratio (SIR) for both sexes. This trend reversed from the 1980s, as in the decade 2000 to 2010 the SIR increased to 1.13 (95% CI, 1.07-1.19) for men and 1.27 (95% CI, 1.12-1.43) for women. In contrast, mortality risk declined for both sexes from the 1960s to the 1990s. The overall risk of BC mortality was also greater for men (standardized mortality ratio [SMR], 1.32 [95% CI, 1.18-1.48]) than for women (SMR, 1.14 [95% CI, 0.80-1.63]). Limitations include possible publication bias, that reports stratify workers mostly by job title not task, that not all studies adjusted for smoking, and that the population was mostly derived from Western nations. Conclusions and Relevance: The profile of contemporary occupations with increased BC risk is broad and differs for incidence and mortality. Currently the incidence seems to be increasing, and this increase is occurring faster in women than men. Improved detection mechanisms and screening are possible reasons for this. Workers with aromatic amine exposure have the highest incidence, while those exposed to polycyclic aromatic hydrocarbons and heavy metals have the greatest mortality