Vertical Distribution and Estimated Doses from Artificial Radionuclides in Soil Samples around the Chernobyl Nuclear Power Plant and the Semipalatinsk Nuclear Testing Site

For the current on-site evaluation of the environmental contamination and contributory external exposure after the accident at the Chernobyl Nuclear Power Plant (CNPP) and the nuclear tests at the Semipalatinsk Nuclear Testing Site (SNTS), the concentrations of artificial radionuclides in soil samples from each area were analyzed by gamma spectrometry. Four artificial radionuclides (²⁴¹Am, ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Co) were detected in surface soil around CNPP, whereas seven artificial radionuclides (²⁴¹Am, ⁵⁷Co, ¹³⁷Cs, ⁹⁵Zr, ⁹⁵Nb, ⁵⁸Co, and ⁶⁰Co) were detected in surface soil around SNTS. Effective doses around CNPP were over the public dose limit of 1 mSv/y (International Commission on Radiological Protection, 1991). These levels in a contaminated area 12 km from Unit 4 were high, whereas levels in a decontaminated area 12 km from Unit 4 and another contaminated area 15 km from Unit 4 were comparatively low. On the other hand, the effective doses around SNTS were below the public dose limit. These findings suggest that the environmental contamination and effective doses on the ground definitely decrease with decontamination such as removing surface soil, although the effective doses of the sampling points around CNPP in the present study were all over the public dose limit. Thus, the remediation of soil as a countermeasure could be an extremely effective method not only for areas around CNPP and SNTS but also for areas around the Fukushima Dai-ichi Nuclear Power Plant (FNPP), and external exposure levels will be certainly reduced. Long-term follow-up of environmental monitoring around CNPP, SNTS, and FNPP, as well as evaluation of the health effects in the population residing around these areas, could contribute to radiation safety and reduce unnecessary exposure to the public.     

Cytogenetic abnormalities of the descendants of permanent residents of heavily contaminated East Kazakhstan

More than 400 nuclear explosion tests were conducted at the Semipalatinsk Nuclear Test Site (SNTS) and significant radioactive substances were released. The long-term consequences of the activities at the SNTS and the appearance of any hereditary effects remain insufficiently studied about 25 years after the test site was closed. The population living in villages near the SNTS are considered to have been heavily exposed to external and internal radiation. This study aims to perform an assessment and comprehensive cytogenetic analysis of the inhabitants living near the SNTS, and their first-(F1) and second-(F2) generation children. Residents of the East Kazakhstan region living in the area covered by the former SNTS were included in the study. To evaluate the hereditary effects of nuclear testing, comprehensive chromosome analyses were performed in lymphocytes using conventional Giemsa and fluorescent in situ hybridization methods in 115 F1 and F2 descendants in the villages of Dolon and Sarzhal, which were heavily contaminated. The parents of the subjects had permanently lived in the villages. A higher number of stable-type chromosome aberrations such as translocations was found in these residents than in 80 residents of the control area, Kokpecty, which indicates the possibility that radiation had biological effects on the exposed subjects.     

Internal exposure to neutron-activated <Superscript>56</Superscript>Mn dioxide powder in Wistar rats—Part 2: pathological effects

To fully understand the radiation effects of the atomic bombing of Hiroshima and Nagasaki among the survivors, radiation from neutron-induced radioisotopes in soil and other materials should be considered in addition to the initial radiation directly received from the bombs. This might be important for evaluating the radiation risks to the people who moved to these cities soon after the detonations and probably inhaled activated radioactive “dust.” Manganese-56 is known to be one of the dominant radioisotopes produced in soil by neutrons. Due to its short physical half-life, ⁵⁶Mn emits residual radiation during the first hours after explosion. Hence, the biological effects of internal exposure of Wistar rats to ⁵⁶Mn were investigated in the present study. MnO₂ powder was activated by a neutron beam to produce radioactive ⁵⁶Mn. Rats were divided into four groups: those exposed to ⁵⁶Mn, to non-radioactive Mn, to ⁶⁰Co γ rays (2 Gy, whole body), and those not exposed to any additional radiation (control). On days 3, 14, and 60 after exposure, the animals were killed and major organs were dissected and subjected to histopathological analysis. As described in more detail by an accompanying publication, the highest internal radiation dose was observed in the digestive system of the rats, followed by the lungs. It was found that the number of mitotic cells increased in the small intestine on day 3 after ⁵⁶Mn and ⁶⁰Co exposure, and this change persisted only in ⁵⁶Mn-exposed animals. Lung tissue was severely damaged only by exposure to ⁵⁶Mn, despite a rather low radiation dose (less than 0.1 Gy). These data suggest that internal exposure to ⁵⁶Mn has a significant biological impact on the lungs and small intestine.     

Endothelial dysfunction in rectal cancer patients chronically exposed to ionizing radiation

We sought to identify the features of endothelial function in rectal cancer patients who were exposed to chronic ionizing radiation from a nuclear test site in Kazakhstan. We examined 146 individuals, 76 of whom were rectal cancer patients. The existence of a complex of disturbances of the endothelium and hemostasis systems in patients vs non-patients was revealed. Endothelial dysfunction was expressed as an increase of nitric oxide (NO) production along with decreases in vasodilatation function, and increased levels of von Willebrand factor in blood, along with an increase in the number of circulating endotheliocytes. Significant correlations between indicators of endothelial function and vascular-platelet hemostasis were observed. These changes and their interrelations were expressed more strongly in the patients who lived in the contaminated area around the nuclear test site. Such patients could have an increased risk of thrombosis and other complications after the treatment of a malignant neoplasm.