## 3 Results  
The results of this study comprise, firstly, the calculation of the absorbed dose through the MCNP6 code for the radionuclide \({}^{137}\)Cs. In particular, the absorbed dose has been estimated as a function of height (distance from the ground) of a typical man (5-180 cm) for the surface activity values of 37, 555, 1480 and 3700 kBq/m\({}^{2}\), respectively and for the exposure time of a week. These results are depicted in Figure 2.  
As can be seen, when the height (distance from the source) is increased, an exponential decrease in absorbed dose occurs. In addition, 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. On the other hand, the dose becomes quite constant after the first 80 cm from the ground, with surface activity of 3700 kBq/m\({}^{2}\), and after the first 30 cm for the corresponding values of 555 and 1480 kBq/m\({}^{2}\), while it is constantly near zero for the value of 37 kBq/m\({}^{2}\); this was expected, since the aforementioned values of distance are within the range of gamma rays in the air [65]. It is of note that the estimated doses for the deposition density of 37 kBq/m\({}^{2}\), as the limit of the high radiation control safe zone according to the UNSCEAR 2000 Report [58] for the Chernobyl nuclear accident, are in the range of 1.1\(\times\) 10\({}^{-4}\)-1.99 \(\times\) 10\({}^{-2}\)--mGy and are considered as \"low absorbed doses\". Next, we present our results of the MCDS for the calculation of the DSB and SSB damage (number of lesions per cell) (Figure 3a,b) for the same values of deposition densities of \({}^{137}\)Cs and for the exposure time of one week. The first thing to note is that the analogy between SSBs and DSBs seems to be in the range reported in irradiated typical mammalian cells [66]. It can also be noted that, for the higher value of surface activity, an exponential decrease is observed in both the numbers of the expected DNA lesions (DSBs and SSBs per cell) of the cell target as a function of distance (height) from the source of \({}^{137}\)Cs. For the value of 1480 kBq\(\cdot\)m\({}^{-2}\) the corresponding numbers show a small decrease at the first 30 cm, while for the other two (and lesser) values of deposition density, the number of the lesions is quite stable as the distance from the source is increased. This means that for the highest value of surface activity, i.e., for a man standing on the ground, exposed to \({}^{137}\)Cs radiation in the near zone (<100 km from the place of the nuclear accident), the number of induced SSBs and DSBs in the cells of his genitals and the rest of his body organs are quite the half of those induced to the cells of his feet. For places in the far zone (100 km to approximately 2000 km), the number of the same lesions is low and quite stable throughout his whole body. It is of note that as the distance from the source increases (and consequently the absorbed dose is reduced), the number of the expected SSBs per cell for the deposition density of 3700 kBq\(\cdot\)m\({}^{-2}\) decreases by a factor of 2.5, reducing, in this way the biological effects of radiation; the corresponding decrease in DSBs with distance is lesser, since this kind of lesion is more complex than SSBs and occurs more scarcely. All our MCDS simulations have been performed with a standard error of the mean better than 0.2%. DSBs are considered to be the most biologically deleterious lesions, since one single unrepaired DSB can lead a cell death or can cause chromosomal aberrations with subsequent genomic instability, and possible malignant transformation [67]. Therefore, this kind of damage was chosen to be analysed mainly in association with the aforementioned results.