Occupational Exposure to Polycyclic Aromatic Hydrocarbons and the Risk of Upper Gastrointestinal Cancers: a Systematic Review and Meta-Analysis of Cohort Studies

Polycyclic aromatic hydrocarbons (PAHs) are environmental and occupational risk factors for some cancers. We conducted a systematic review and meta-analysis on the risk of upper gastrointestinal cancers, including esophageal and gastric cancers, among workers exposed to PAHs. We searched PubMed, EMBASE, and SCOPUS through December 2024, as well as International Agency for Research on Cancer Monographs and reference lists, for cohort and nested case-control studies. Relative risks (RRs) and odds ratios were pooled using random-effects models. Heterogeneity was assessed with the I2 statistic. Subgroup analyses were conducted by sex, region, industry type, study quality, and publication year. Duration of exposure-response was evaluated using meta-regression. Twenty-seven studies met the inclusion criteria, comprising diverse high-exposure occupations including coke production, aluminum production, metalworking, and chimney sweeping. Overall, occupational PAH exposure was associated with an increased risk of upper gastrointestinal cancers [relative risk (RR) = 1.23, 95% confidence interval (CI): 1.10-1.38]. For esophageal cancer, the pooled RR was 1.31 (95% CI: 1.05-1.63), with higher risk estimates observed in high-exposure occupations. Gastric cancer showed a modestly elevated risk (RR = 1.19, 95% CI: 1.05-1.35). Meta-regression indicated a positive association between duration of exposure and esophageal cancer risk (RR per year = 1.03, 95% CI: 1.01-1.06), but not for gastric cancer. No evidence of publication bias was detected ( P  = 0.66 for esophageal and P  = 0.33 for gastric cancer). Occupational PAH exposure is modestly associated with upper gastrointestinal cancer risk, particularly esophageal cancer. Residual confounding and other sources of bias cannot be excluded, preventing conclusions in terms of causality.