Occupational exposure to metal welding and cataract: A systematic review and meta-analysis

BACKGROUND: Metal welding generates ultraviolet radiation (UVR) of cataractogenic wavelengths, and UVR emitted during welding has been associated with cataract formation, but results from prior studies are conflicting.

METHODS: We conducted a systematic review and meta-analysis of epidemiological studies addressing associations between occupational metal welding and cataract. The literature search was conducted on November 15, 2023, across seven literature databases. Studies comparing age-adjusted occurrence of cataract among welders and control groups were included. Two reviewers extracted data, which were combined using random-effects meta-analyses.

RESULTS: We identified nine studies with a total of 5165 welders and 513 026 controls. There was considerable heterogeneity among studies (I2 statistics: 39), and possible publication bias in favour of higher risk estimates. Stratified meta-analyses revealed a summary OR of 1.22 (n = 3, 95% CI 0.79-1.90; p = 0.374) for cataract among welders in high-income countries, whereas the OR was 2.95 (n = 9, 95% CI 1.68-5.19; p = 0.00017) in lower-middle-income countries.

CONCLUSION: An increased risk of cataract among welders was found in studies from lower-middle-income countries, but not in studies from high-income countries. The disparity could reflect differences in occupational safety adherence and study methodology and may also involve effect modification by cumulative solar UVR. Although a causal link between UVR from metal welding and cataract is biologically plausible, epidemiological evidence is still limited. More studies are needed to quantify the exact risk of cataract among welders in various populations.