Low-dose radiation exposure and risk of self-reported cataract in Fukushima nuclear emergency workers

Background Cataract is a well-established radiogenic condition and recent evidence suggests an increased risk even at radiation doses of <100 mGy. Following the 2011 Fukushima Daiichi Nuclear Power Plant accident, ∼20 000 workers participated in emergency operations. This study aimed to investigate the association between cumulative low-dose occupational radiation exposure and the risk of cataract among workers enrolled in the Epidemiological Study of Health Effects in Fukushima Nuclear Emergency Workers. Methods Data from 5773 nuclear emergency workers participating in the cohort were analysed. The cumulative lifetime occupational radiation dose was estimated by combining pre-2011 individual dose records from a nationwide nuclear radiation worker dose registry with radiation doses received during the 2011 emergency-work period. Self-reported, physician-diagnosed cataract was identified through baseline and first follow-up questionnaires. A Cox proportional hazards model was applied to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for incident cataract, with adjustments for major covariates. Results More than 90% of the participants had cumulative occupational radiation exposure of <100 mSv, including doses received both prior to the accident and during the emergency period (March–November 2011). During 52 921 person-years of follow-up from 2012 to 2024 (mean, 9.2 years), 310 participants reported new-onset cataract. The risk of cataract increased with lifetime occupational exposure up to November 2011, with an HR of 1.03 per 10-mSv increase (95% CI, 1.02, 1.05). This association persisted after excluding participants with doses of ≥100 mSv. For exposure during the emergency period (March–November 2011), the HR was 1.06 per 10-mSv increase (95% CI, 1.03, 1.09). When the cumulative lifetime occupational radiation dose was recalculated by using 2-year and 5-year lag periods before diagnosis or censoring, the HRs per 10-mSv increase were 1.03 (95% CI, 1.01, 1.04) and 1.01 (95% CI, 0.99, 1.04), respectively. Conclusion This study suggests an excess risk of cataract at doses of <100 mSv and adds to the evidence base suggesting an association between low-dose occupational radiation exposure and cataract risk.