Occupational benzene exposure and risk of head and neck cancer: A systematic review and meta-analysis

Introduction: Benzene, an aromatic hydrocarbon, is a well-known leukemogen. To date, the link between benzene exposure and solid cancers is under examination. Our objective is to perform a systematic review and meta-analysis to evaluate if the occupational exposure to benzene is associated with the incidence and mortality of head and neck cancers (HNCs). Methods: We systematically reviewed the literature for pertinent cohort studies mentioned in the most recent IARC Monograph on benzene working exposure and other cohorts and case-controls identified via a literature search performed in PubMed, Scopus, and Embase, from their inception to March 2024. Stratified multilevel meta-analyses according to study design, cancer type, industrial sector, quality score of the articles, geographic region and risk of exposure bias were conducted. Results: A total of 29 independent studies were included in our review and multilevel meta-analysis. The findings revealed a bordeline association between exposure to occupational benzene and incidence of HNCs RR = 1.27, 95% CI = 1.00–1.64, I² level2 = 0%, I²level3 = 43.30%, P < 0.05). In addition, we found a significant increased overall risk of HNCs in females (RR = 1.68, 95% CI = 1.07–2.61; I²level2 = 0%, I²level3 = 0%, P = 0.433). Stratification analysis according to cancer sites showed a significant increase in risk of nose & sinuses cancers (RR = 3.72, 95% CI = 2.07–6.68; I²level2 = 34.13%, I²level3 = 0%, P = 0.17). European cohorts (RR = 1.31, 95% CI = 1.08–1.59, p < 0.01) and lower quality studies (RR = 1.39, 95% CI = 1.00–1.91; I²level2 = 0%, I²level3 = 45.94%, P < 0.001). No evidence of publication bias was found (Egger test P = 0.103). Conclusions: In conclusion, this systematic review and meta-analysis provide evidence that workers with occupational exposure to benzene might be at increased risk of HNCs, in particular for nose & sinuses cancer. However, it is essential to consider the limitations of the studies, particularly residual confounding, and the areas that need further study to improve our understanding of the subject.