Occupational Exposure to Benzene and Risk of Breast Cancer: Systematic Review and Meta-Analysis

Introduction: Benzene is a recognized carcinogen; however, its association with breast cancer is not well established. Hence, a meta-analysis of cohort and case-control studies was performed to determine the association between occupational benzene exposure and the risk of breast cancer. Methods: A systematic literature review identified 7573 publications from which 23 cohort and case-control studies were retained and evaluated using meta-analyses (random effects model). PRISMA guidelines were followed. Our protocol was registered in the PROSPERO database (Registration No. CRD42022379720). Study quality was assessed using a modified Newcastle-Ottawa scale (NOS). Results: The summary relative risk (RR) for ever-benzene exposure was 1.17 (95% CI=1.061.28, I2=38.6%,p=0.032, n=23 risk estimates); corresponding RR for cancer incidence and mortality were 1.17 (95% CI=1.05-1.29, I2=56.1%,p=0.003, n=16) and 1.09 (95% CI=0.86-1.38, I2<0.001%,p=0.96, n=10). However, heterogeneity was not detected for publication year (p-het=0.10), study design (p-het=0.78), study quality (p-het=0.06), and industry of employment (p-het=0.86). The RR for a high level of exposure showed a positive association with breast cancer 1.35 (95% CI=1.06-1.72, I2 =<0.001%,p=0.65, n=3) and (P-het=0.87). Publication bias was detected (p=0.03). Conclusions: The results of our meta-analysis indicate a positive association between occupational benzene exposure and an increased risk of breast cancer, particularly when exposed to higher levels of benzene. However, bias and confounding could not be excluded.