The Essence of Radiogenic Damages in the Lens: Threshold, Tissue Reactions (Deterministic Effects), but not Stochastic, Non-Threshold Effects

The purpose is to analyze the arguments ‘for’ and ‘against’ the assumption that radiogenic disturbances in the lens, previously considered as tissue reactions with a threshold (deterministic effects), may be stochastic events characterized by the absence of a threshold. The importance of the nature of radiation cataractogenesis for radiation safety is associated with the conceptual difference in approaches to developing Radiation Safety Standards. For threshold effects, Radiation Safety Standards with dose limits not exceeding the threshold is sufficient for 100 % protection, while for stochastic events, protection is based on the concept of ‘socially admissible risk’, since the probability of an effect exists at any radiation dose. An analysis of four arguments in favor of the non-threshold and stochastic nature of radiogenic disturbances in the lens demonstrated that some considerations may not be relevant to the problem (such as the lack of a dose rate effect, which may be explained by the lack of DNA repair and cellular renewal in the lens). An attempt to justify the absence of a threshold of less than one by the value of the upper confidence interval for the risks in the cohort of victims of the atomic bombings is untenable based on the canons of statistics and epidemiology. Data on the effects of low-dose low-LET radiation (up to 0.1 Gy) on lens abnormalities are lacking for most study populations, and for those that have been reported (medical radiologists, industrial radiographers, and patients undergoing computed tomography), the results are inconsistent, non-system, and can be explained, among other things, by non-radiation factors. The last argument ‒ the molecular cellular prerequisites for the stochastic hypothesis (the presence of only a hypothetical biological mechanism) does not have direct evidentiary force in the field of epidemiology. At the same time, there are strong arguments for the deterministic nature of radiogenic disorders in the lens. The main effect is the influence of the radiation dose on the severity of the pathology, which is typical only for tissue reactions. Experimental, epidemiological and environmental examples of dose dependencies for radiogenic disorders in the lens are presented, which cover almost all irradiated groups and conditions: effects on animals and people; radiation of different quality ‒ both low and high LET; for professional contingents, patients and residents of radioactively contaminated areas. Another argument is the long-term identification of threshold doses, both in laboratory and in epidemiological studies (from 2011–2012 to the present, the threshold is a dose of 0.5 Gy according to the ICRP and UNSCEAR). Based on these ICRP regulations, acceptable standards for lens irradiation were formed for professionals and the public. The presented analytical study summarizes the discussion about the nature of radiogenic disorders in the lens: according to the totality of various correct data, these are threshold, tissue reactions (deterministic effects).