Previous systematic reviews have adopted binary exposure classifications without characterizing the heterogeneity of welding fume exposures. We aimed to estimate lung cancer risk from welding fumes with systematic exposure characterization by process type, base material, and metal fume component, and to examine evidence for related high-temperature processes. We searched PubMed, Embase, and Web of Science through July 2025 for cohort, case-control and other epidemiological studies. Exposure information was systematically extracted from full-text descriptions and classified by welding process, base material, and metal fume component. Separate random-effects meta-analyses were performed for comparative risk and standardized ratio estimates. Of 86 studies meeting inclusion criteria, 58 were included in quantitative synthesis after excluding 12 overlapping cohorts and 16 high-risk-of-bias studies; 39 comparative risk and 22 standardized ratio studies were analyzed. The pooled relative risk was 1.51 (95% CI: 1.36–1.67; I2 = 39.4%) and standardized ratio was 1.32 (95% CI: 1.24–1.40; I2 = 76.6%). The association was robust across subgroup analyses: studies adjusting for smoking (RR = 1.55; n = 31) and asbestos (RR = 1.53; n = 12) yielded estimates consistent with the overall finding. A significant dose-response gradient was observed for both comparative risk (p = 0.03) and standardized ratio studies (p = 0.013). Gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) showed elevated point estimates, with stainless steel welding showing suggestive evidence of increased risk; however, secondary analyses were based on few studies with wide confidence intervals. Evidence of publication bias was detected but adjusted estimates remained significant. Evidence certainty was moderate for comparative risk and low for standardized ratio estimates. Welding fume exposure is associated with approximately 50% increased lung cancer risk, with consistent sensitivity analyses. Process-specific analyses suggest elevated risks for GMAW and stainless steel welding, though based on limited data, warranting further investigation alongside prioritized prevention efforts. Data on brazing, soldering, and flame cutting were limited, representing evidence gaps for future research. PROSPERO CRD420251238410
Kim et al. (Mon,) studied this question.