Abstract
This is the first study of cataract incidence in a cohort of Mayak Production Association workers first employed at one of the main facilities in 1948–1982 and followed up till the end of 2008 (22,377 workers). Principal advantages of the study are the large size of the cohort, long-term follow-up and sufficient statistical power, available results of annual eye examinations over the entire follow-up period and detailed information on non-radiation confounders. Individual measured doses from external γ-rays and neutrons used in the analyses were provided by the Mayak Worker Dosimetry System 2008 (MWDS-2008). Relative risk (RR) and excess relative risk (ERR) per unit dose (Gy) were calculated based on maximum likelihood using the AMFIT module of the EPICURE software. The RR of cataract incidence was found to be the highest in workers exposed at doses above 2.0 Gy. A significant linear association of cataract incidence with cumulative dose from external γ-rays was found with ERR/Gy equal to 0.28 (95% confidence intervals: 0.20, 0.37). The results obtained varied slightly with inclusion of additional adjustments for non-radiation factors (smoking index, hypertension, glaucoma and body mass index). Adjusting for the dose from neutrons gave a considerable increase in ERR/Gy for cataract incidence.
Highlights
Ionizing radiation is known to cause lens opacification [1, 2]
The Relative risk (RR) of cataract incidence was significantly higher in workers with glaucoma (2.951, 95% confidence intervals (CIs): 2.470, 3.496) and myopia (2.073, 95% CI: 1.526, 2.749) compared to workers free from these diseases (2.475, 95% CI: 1.823, 3.274 for glaucoma and 1.926, 95% CI 1.384, 2.601 for myopia)
The present study failed to observe a significant increase in the risk of cataract incidence in females compared to males (RR = 1.013, 95% CI: 0.948, 1.082)
Summary
Ionizing radiation is known to cause lens opacification [1, 2]. Since Publication 26 of the International Commission on Radiological Protection (ICRP), radiation-induced cataracts have been classified as deterministic effects with a dose threshold depending on the rate of dose delivery (acute, fractionated/protracted, or chronic) [3]. Thresholds for radiationinduced cataracts and dose limits for the ocular lens have been updated based on available science [4]. The most recent update was made in 2011 [5] when ICRP recommended reducing the threshold from 5 Gy for acute radiation exposure and >8 Gy for fractionated and protracted exposure down to 0.5 Gy independent on radiation dose rate, given that minor opacities progress to vision-impairing cataracts, and considering that the dose threshold for protracted.
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