###### Abstract
It was also estimated (some months after the accident) that the amount of radioactive materials released into the environment at that time was approximately 10% (1.6 \(\times\) 10\({}^{17}\) Bq for \({}^{131}\)I and 1.5 \(\times\) 10\({}^{16}\) Bq for \({}^{137}\)Cs) that of the Chernobyl accident [24]. Up until now, a large area of a few thousand square kilometres around CNPP (the 'Chernobyl Exclusion Zone') remains evacuated, with restricted human access. \({}^{131}\)I (half-life: 8 days) has long decayed, and \({}^{134}\)Cs (half-life: 2 years) has already been considered depleted, therefore, the main existing problem is the radioactive hazard from contamination by \({}^{137}\)Cs (half-life: 30.17 years), although half of the initial release has now decayed. The whole restricted zone gives the opportunity for the study of radiation transmission to the animals of this area, since wildlife is flourishing in the absence of human activities [25]. In Fukushima, there are confined areas within a radius of 40 km around the FDNPP, where the annual effective dose exceeds 20 mSv (the effective dose limit established by the Japanese Government for the lifting of the human exclusion order) and other areas where the corresponding value is up to 50 mSv. Although remediation measures through the years have been taken for the maximum possible decrease in the radioactive nuclides of the terrestrial area, the radio-contamination levels do not permit the return of evacuees to their land. Gamma-radiation from the deposited \({}^{137}\)Cs still remains a big problem for authorities [26]. As referred to above, the \({}^{137}\)Cs content in these areas is also investigated through lichens and other plants [27]. As also occurred in Chernobyl, \({}^{90}\)Sr dispersion over the Fukushima territory was limited and the biggest part of this released radionuclide was deposited in the proximity of the FDNPP [19]. One of the main pathways leading to human exposure after such a REI is the external exposure from radionuclides deposited on the ground [28]. Gamma-radiation from these radionuclides has been a major contributor to the external exposure of the public due to a nuclear accident [29]. In our study, we focus on the \({}^{137}\)Cs as the most prominent radionuclide for ground contamination due to its substantial contribution to the lifetime effective dose to humans, its long radioactive half-life, and its ease of measurement. Exposure to IR induces a range of DNA lesions to living cells. IR photons especially can target the nuclear DNA molecule in two ways: either by directly striking it, with the induction of secondary electrons, causing breaks in the phosphodiester bond connecting adjacent nucleotides on the same side of the DNA helix, or by water radiolysis, which can result in the formation of reactive oxidative species (ROS) and additional oxidative DNA damage. All the above can result in the formation of simple or complex lesions [30; 31]. In such a DNA lesion, a single nucleotide is characterized by an abnormal chemical alteration, i.e., a missing or damaged base or a strand break. These lesions may comprise base damage (BD), single-strand breaks (SSBs, i.e., a cluster of lesions that contains at least one strand break and which has no other additional break within 10 bp on the opposed strand), double-strand breaks (DSBs, i.e., this is a lesion that consists of two SSBs, which are located on opposite strands within 10 bp of each other) and complex DNA damage (groups of several lesions within 1 or 2 helical turns of the DNA molecule) [32]. Among them, DSBs and non-DSB clustered damage (i.e., two or more lesions within one or two helical turns of DNA induced by the passage of a single radiation track) [33] are considered to be the primary cause of radiation-induced cell killing, mutagenesis and neoplastic transformation. Through the process of breaking and re-joining, DSBs are converted into small- or large-scale chromosomal exchanges with the ability to induce phenotypic tumor lesions and, finally, cell death.