Abstract
In this paper, we present a useful Monte Carlo (MC)-based methodology that can be utilized to calculate the absorbed dose and the initial levels of complex DNA damage (such as double strand breaks-DSBs) in the case of an environmental ionizing radiation (IR) exposure incident (REI) i.e., a nuclear accident. Our objective is to assess the doses and complex DNA damage by isolating only one component of the total radiation released in the environment after a REI that will affect the health of the exposed individual. More specifically, the radiation emitted by radionuclide 137Cs in the ground (under the individual’s feet). We use a merging of the Monte Carlo N-Particle Transport code (MCNP) with the Monte Carlo Damage Simulation (MCDS) code. The DNA lesions have been estimated through simulations for different surface activities of a 137Cs ground-based γ radiation source. The energy spectrum of the emitted secondary electrons and the absorbed dose in typical mammalian cells have been calculated using the MCNP code, and then these data are used as an input in the MCDS code for the estimation of critical DNA damage levels and types. As a realistic application, the calculated dose is also used to assess the Excess Lifetime Cancer Risk (ELCR) for eight hypothetical individuals, living in different zones around the Chernobyl Nuclear Power Plant, exposed to different time periods at the days of the accident in 1986. We conclude that any exposition of an individual in the near zone of Chernobyl increases the risk of cancer at a moderate to high grade, connected also with the induction of complex DNA damage by radiation. Generally, our methodology has proven to be useful for assessing γ rays-induced complex DNA damage levels of the exposed population, in the case of a REI and for better understanding the long-term health effects of exposure of the population to IR.
Highlights
We have developed an efficient computational method with the combination of a small-scale Monte Carlo (MC) biophysical model (MCDS), with a larger-scale and general-purpose MC transport code (MCNP) to reproduce the results induced in the cell environment after such an exposure
An initial sharp decrease in the slope of the curve is observed at small heights on the water phantom; this happens because an increase in the distance from the source is equivalent to the reduction in the number of photons which penetrate a surface along the direction of the radiation
More analytically, the first calculation is about an adolescent, 16 years old at the year of the Chernobyl nuclear accident, exposed to a 30-day irradiation because his family—for various reasons—delayed to evacuate their homestead in the near zone of 3700 kBq·m−2 : assessing a total dose of 3.44 mGy for all those days of exposure, we evaluate an Excess Lifetime Cancer Risk (ELCR) for his prostate gland equal to 3.91 × 10−5, which is considered high according to the World Health Organization [99], the Canadian Council of Ministers of the Environment [100] and the New Zealand Ministry for the Environment [101]
Summary
Large-scale exposure to IR, in terms of both the amount of radiation and the number of people exposed occurs rarely due to international safeguards that are currently in force. All the nuclear accidents that have taken place have provided us with valuable information and experience about the health consequences of the leaked radioactivity to the public and the appropriate health management of such incidents. April 1986, as the first large-scale REI, has been a great challenge to the scientific community that deals with the radiation protection, to revise much of its knowledge until that time and to improve the relevant nuclear safeguard rules. The value of the experience gained from that nuclear accident found application [1] to other accidents that followed of a smaller scale, such as in Brazil (the Goiânia 137 Cs accident in 1987) and the two accidents that took place in Tokaimura of Japan on 11 March 1997 and 30 September 1999 [2,3], as well as of a larger scale, as with the accident that too place in Fukushima Daiichi on 11 March 2011 [4]
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