Ionizing radiation can deposit energy in a system and it is ubiquitous in the environment. Its source can be natural such as radioactive materials and cosmic rays or artificial, such as nuclear power plants [10]. Recently, there has been a strong interest in the health of organisms in radioactively contaminated sites such as those of Chernobyl and Fukushima Dai-ichi. Many wildlife species have surprised many scientists, but there are also reports of significant effects of chronic irradiation at relatively very low doses ^[11][12][11,12]. This contradiction has been observed at doses of environmental radioactivity and has yet to be fully understood. It is important to do this because ionizing radiation, although present in nature, can also derive from human activities. The exposure of a biological system to ionizing radiation activates a series of signals that start with the absorption of energy and continue in biological lesions [13]. There are two types of interactions, direct and indirect. In direct, the energy of the radiation is deposited directly in the targets. In indirect actions, on the other hand, the energy is first absorbed by an external medium, leading to the production of diffusible intermediates which subsequently attack the targets. The main target in both interactions of ionizing radiation is the H₂O molecule, present in all organisms ^[11][14][11,14]. The primary reactions are excitation and ionization, which produce ionized water molecules (H₂O^•+) and the radicals H^• and ^•OH (Figure 1) ^[11][14][11,14]. In addition, in a biological system this type of ionization is induced along the entire path of the radiation, triggering chain reactions, which produce secondary reactive oxygen species (ROS) because of H^• and e_aq⁻ becoming trapped ^[15][16][15,16]. The most important ROS is H₂O₂; O₂^−• is produced in low doses, based on molecular oxygen levels. The •OH radical can react very quickly with different types of macromolecules including lipids and proteins, but especially with Deoxyribonucleic Acid (DNA) ^[11][15][16][11,15,16]. However, depending on the dose, many of the resulting injuries can be readily mitigated and repaired. Radio-induced DNA damage is mainly caused by indirect effects and is considered the most important, although direct effects may contribute to the damage [17]. Consequently, based on the dose and radio-sensitivity of the species, both genomic and chromosomal aberrations are generated. Generally, DNA is a candidate to be the primary site of radiation damage, thus explaining the resulting radiation-induced mitotic arrest ^[17][18][17,18]. Furthermore, there are cellular mechanisms that allow damaged cells to repair the damage; however, errors in DNA repair naturally occur and this leads to aberrations and subsequent transmission to descent ^[19][20][19,20]. Thus, cell division in the meristem or germline responds drastically to ionizing radiation. It is difficult to compare current data on plant responses to ionizing radiation as the conditions of the models and parameters of past experiments are very different [21]. Therefore, the type of irradiation (acute or chronic), the dose rate or dose applied, the physiological parameters such as species, varieties, cultivars considered, the stage of development at the time of irradiation and the variations of the individual could be different between studies. The current inhomogeneity is further aggravated by the coexistence of different experimental data, data applied by the food industry and data relating to accidents ^[22][23][22,23]. Consequently, in the experimental field of plant radiation, doses can vary from a few Gy to several hundred Gy but can also reach the level of kGy. Furthermore, the dose range response strongly depends on the species studied. It is difficult to predict a standard response to ionizing radiation in plants even though promising standardization schemes are emerging ^[11][22][24][11,22,24].

The effects of ionizing radiation in higher plants are of interest to agriculture, ecology, health, and new space frontiers ^[11][12][11,12]. In general, four fundamental aspects of plant biology need to be considered as they provide a vital context for analyzing the effects of ionizing radiation [22]. The light reactions of photosynthesis start with photolysis of H₂O; consequently, this process produces large quantities of ROS, the same products of H₂O radiolysis that plants are generally able to block thanks to the large production of antioxidants [25]. It must be considered that in multicellular plants, cells divide into meristematic tissues, and they have quiescent centers with the same functionality as stem cells but are not identical to each other ^[11][22][11,22]. For example, they lack the apoptotic response of animal stem cells, mediated by the p53-oncoprotein. Meristems in plants are a biologically distinct product resulting from an independent evolution of multicellularity; the effects of ionizing radiation on them are not yet well known [22]. It is important to note that the meiotic divisions that produce the generation of gametophytes in the reproductive organs of plants are separated in each generation by many divisions of vegetative cells in the generation of sporophytes; in detail, the plants alternate between generations and no dedicated germ line [26]. Although tumors can occur in plant tissues, thanks to multiple controls on dividing plant cells and the low probability of metastasis, being organisms without a circulatory system, plants do not suffer the oncogenesis effects, typical of many animals [22]. Hence, plants are unlikely to have the same stochastic effects as ionizing radiation in animals, where in many cases they cause carcinogenesis [22]. Therefore, the current information on the effects of ionizing radiation on multicellular organisms is provided by the knowledge of the effects on organisms with lower antioxidant capacity than plants, which possess stem cells and germ lines without equivalent in plants and which suffer from stochastic effects that probably do not occur in the plant kingdom ^[11][22][27][11,22,27].

3. Current and Future Perspectives: Management in the Medical Field

Research into the long-term effects on flora, fauna and human health following the FNPP incident is constantly evolving and proceeding relentlessly [7]. The CNPP and FNPP accidents provide unique opportunities on the investigation of radiological consequences and radiation effects on environment in a large scale that cannot be observed in the laboratory, not only for the health of higher plants but also for human health ^{[28][29][30][31][32]}[32,44,45,46,47]. Prior to the Fukushima incident, few decision makers paid attention to the need to plan health investigations following a large-scale radiation scattering incident ^[32][33][34][47,48,49]. Following the FNPP incident, despite the serious initial difficulties, the basic concept of the Fukushima Health Management Survey (FHMS) was developed, which defined not only the health effects of ionizing radiation, but also other problems, such as example mental health and the consequences of long-term relocation ^[35][36][50,51]. To cope with this emergency, SHAMISEN (Nuclear Emergency Situations—Improvement of Medical and Health Surveillance) was founded in 2016 and its activities are still largely active today ^[35][50]. It is a project funded by the Open Project For European Radiation Research Area, that aims to develop recommendations for medical and health surveillance of populations affected by previous and future radioactive incidents based on lessons learned from past incidents, including the CNPP and FNPP incidents ^[35][37][38][50,52,53]. SHAMISEN recommendations state that: “The management of radiological incidents also raises important ethical questions. Although most radiation protection actions, including health surveillance, are aimed at reducing the impacts of exposure to ionizing radiation, most of them lead to with it a multitude of direct and indirect consequences that can have a great impact on the well-being of the affected populations. Ethical considerations are also important for the design and implementation of health surveillance and epidemiological studies” ^[35][37][38][50,52,53]. In conclusion, given the purpose and current activity of SHAMISEN, it is currently, proving to be a useful tool to better manage future large-scale incidents with dispersion of ionizing radiation ^[37][38][52,53]. Ensuring a precise, targeted, and fast intervention in the management of emergencies is the ultimate goal of decision makers. Learning from past incidents and implementing this knowledge can make a significant difference in terms of lives and costs in healthcare management ^[39][54].