Cataractogenic Effects оf Low-Dose Radiation with Low LET: More not Than There. Report 1. Statement оf тhe Problem аnd Experiments оn Animals

Abstract

Radiation disturbances in the lens are considered as the third most important effects of radiation, after mortality from cancer and diseases of the circulatory system (ICRP-118). In terms of the problem of the effects of low doses radiation with low LET (up to 100 mGy), interest in the dose relationship for the induction of disturbances in the lens after irradiation increases in a linear progression, as evidenced, among other things, by the chrono-dynamics of the increase in the number of relevant reviews by years shown here (since 2007; r = 0.650; p = 0.006). However, there is still no clarification of the question of the evidence of the effect of low doses on the lens. This study, consisting of two reports, attempts to fill this gap. Since epidemiological associations to confirm causality should, if possible, meet the criterion of “Biological plausibility”, this Report 1 reviewed the work considered in thematic publications on the cataractogenic effects of the lowest doses of radiation with low LET in experiments in vitro and in animals. The extreme radiosensitivity of the lens cells, exceeding even the parameters of lymphocytes in terms of induction of DNA double-strand breaks, is confirmed in a number of works (an increase in the level of breaks is shown even for a dose of 20 mGy). However, when the dose regularities are transferred to the irradiation of mice and rats in vivo, the conclusions about the effects of low doses are not confirmed. A sample of works over more than 70 years did not reveal such effects. The three exceptions (not included in PubMed paper cited in a single source, a workshop presentation, and an arbitrary textbook mention without citation) do not serve as valid scientific sources. The singularity of these data does not fall under the criterion “Consistency of association”. The smallest threshold doses of radiation for the induction of cataractogenic effects in mice are, according to studies as early as the 1950s, ~114 mGy and ~140 mGy for X-rays. The value of 150 mGy is also called (Shafirkin A.V., Grigoriev Yu.G., 2009). However, one should adhere to the results of more recent studies, according to which, when exposed to radiation in mice, a tendency to opacity in the lens can be observed for a dose of 0.2 Gy, with a statistically significant fixation of the effect for a dose of only 0.4 Gy. Most sources in experiments on rodents report threshold doses in units of gray, with a minimum of 0.5 Gy. Thus, the effects of low doses on the lens opacity were not found in the experiment.