Awareness of the implementation of stable iodine prophylaxis by parental guardians living in the urgent protective action planning zone of an operating nuclear power plant in Japan

Purpose The aim of this study was to clarify the characteristics and awareness of the need for protection against ionizing radiation, such as sheltering, evacuation, and implementing stable iodine prophylaxis, of guardians parenting young children living in an urgent protective action planning zone (UPZ) of an operating nuclear power plant in Japan. Methods Self-administered questionnaires were distributed to approximately 3000 guardians through 26 kindergartens located within a UPZ. Responses were obtained from 1172 who lived in the UPZ and were included in the analysis. Results Of the 1172 guardians, 460 (39.2%) responded that sheltering is not useful to reduce the dose of radiation exposure. On the other hand, 395 (33.7%) guardians responded that implementing stable iodine (SI) prophylaxis could prevent exposure from all radionuclides, and 876 (74.7%) responded that pregnant women should also implement SI prophylaxis in a nuclear emergency. Furthermore, 83.0% (973) responded that they wanted to receive pre-distribution of stable iodine (PDSI) for their children. On the other hand, 38.9% (456) of guardians had not known about SI before the study, and 71.8% (841) of guardians felt anxious about implementing SI prophylaxis for their children. Conclusion Most guardians had expectations regarding SI and received PDSI, but they felt anxious about implementing SI prophylaxis for their children. It is essential that guardians living in the UPZ of restarted nuclear power plants be educated, and that risk communication about protection against ionizing radiation, including the side effects of implementing SI prophylaxis and radiation health effects, be conducted.

A comparison of thyroidal protection by iodine and perchlorate against radioiodine exposure in Caucasians and Japanese

Radioactive iodine released in nuclear accidents may accumulate in the thyroid and by irradiation enhances the risk of cancer. Radioiodine uptake into the gland can be inhibited by large doses of stable iodine or perchlorate. Nutritional iodine daily intake may impact thyroid physiology, so that radiological doses absorbed by the thyroid as well as thyroid blocking efficacy may differ in Japanese with a very rich iodine diet compared to Caucasians. Based on established biokinetic–dosimetric models for the thyroid, we derived the parameters for Caucasians and Japanese to quantitatively compare the effects of radioiodine exposure and the protective efficacy of thyroid blocking by stable iodine at the officially recommended dosages (100 mg in Germany, 76 mg in Japan) or perchlorate. The maximum transport capacity for iodine uptake into the thyroid is lower in Japanese compared to Caucasians. For the same radioiodine exposure pattern, the radiological equivalent thyroid dose is substantially lower in Japanese in the absence of thyroid blocking treatments. In the case of acute radioiodine exposure, stable iodine is less potent in Japanese (ED50 = 41.6 mg) than in Caucasians (ED50 = 2.7 mg) and confers less thyroid protection at the recommended dosages because of a delayed responsiveness to iodine saturation of the gland (Wolff–Chaikoff effect). Perchlorate (ED50 = 10 mg in Caucasians) at a dose of 1000 mg has roughly the same thyroid blocking effect as 100 mg iodine in Caucasians, whereas it confers a much better protection than 76 mg iodine in Japanese. For prolonged exposures, a single dose of iodine offer substantially lower protection than after acute radioiodine exposure in both groups. Repetitive daily iodine administrations improve efficacy without reaching levels after acute radioiodine exposure and achieve only slightly better protection in Japanese than in Caucasians. However, in the case of continuous radioiodine exposure, daily doses of 1000 mg perchlorate achieve a high protective efficacy in Caucasians as well as Japanese (> 0.98). In Caucasians, iodine (100 mg) and perchlorate (1000 mg) at the recommended dosages seem alternatives in case of acute radioiodine exposure, whereas perchlorate has a higher protective efficacy in the case of longer lasting radioiodine exposures. In Japanese, considering protective efficacy, preference should be given to perchlorate in acute as well as prolonged radioiodine exposure scenarios.

Risk perception of the pre-distribution of stable iodine to guardians of children living around the Genkai Nuclear Power Plant, Saga Prefecture, Japan

Iodine thyroid blocking (ITB) is effective for preventing childhood thyroid cancer when radioactive iodine is released into the environment during a nuclear power plant accident. Japan employs the pre-distribution of stable iodine (PDSI) to residents living near nuclear power plants; however, the number of residents who have actually received stable iodine to date remains limited. The aim of this study was to evaluate the profile of guardians of children living around the Genkai Nuclear Power Plant (GNPP) in Japan. We distributed self-administered questionnaires regarding perception of risks associated with administration of stable iodide to approximated 400 guardians of children aged 0–6 in 10 kindergartens located in four municipalities. We obtained responses from 286 guardians, and after excluding invalid responses, 247 were included in the analysis. Logistic regression analysis revealed that living within 5 km of the GNPP (odds ratio [OR] = 4.48, 95% confidence interval [CI]: 2.43–8.24), awareness of preferential implementation of ITB to children (OR = 3.33, 95%CI: 1.78–6.22), and awareness of the prophylaxis booklet published by the local government (OR = 2.53, 95%CI: 1.37–4.68) were independently associated with PDSI for children. The main reasons for not receiving PDSI were “anxiety about the side effects of stable iodine” (40.2%), “distrust of the effectiveness of SI” (23.5%), “complicated procedures for receiving stable iodine” (15.7%) and “missed the date for receiving stable iodine” (8.8%). In the case of ITB implementation during a nuclear emergency, it is necessary to clarify the risk perceptions of guardians and adapt risk communication accordingly.

Characteristics and recognition of guardians living in the urgent protective action planning zone of the Genkai Nuclear Power Plant, Saga Prefecture, Japan who wished to receive pre-distribution stable iodine for their children

Purpose：The aim of this study was to clarify the characteristics and the awareness of nuclear prevention measures including prophylactic stable iodine (SI) of guardians of 0- to 6-year-old children living in the urgent protective action planning zone (UPZ) of the Genkai Nuclear Power Plant (GNPP), Japan. Methods：Of these 1172 guardians, 973 responded that they wished to receive pre-distribution of stable iodine (PDSI) and 199 did not wish to receive PDSI. Results: Logistic regression analysis showed that the following items were independently associated with guardians who wished to receive PDSI for their children: thinking that pregnant women should take prophylactic SI (odds ratio [OR]=6.57, 95% confidence interval [CI]: 4.62–9.35; p<0.01); wishing to participate in a lecture about the health effects of radiation exposure (OR=1.99, 95%CI: 1.40–2.82; p<0.01); thinking that SI can prevent exposure from all radionuclides (OR=1.93, 95%CI: 1.24–2.99; p<0.01); awareness of SI before the study (OR=1.91, 95%CI: 1.35–3.00; p<0.01); and anxiety about prophylactic SI for their children (OR=0.33, 95%CI: 0.20–0.55; p<0.01). The GNPP was one of the nuclear power plants in Japan that resumed operations after the Fukushima Dai-ichi Nuclear Power Plant accident in 2011. Conclusion: These results suggest that some residents have incomplete knowledge about nuclear prevention, including SI. Therefore, it is essential to educate residents and communicate the health risks of radiation exposure with residents living around nuclear power plants. Furthermore, it is important to train specialists to educate and communicate with residents to prepare for a nuclear accident.

No significant association between stable iodine intake and thyroid dysfunction in children after the Fukushima Nuclear Disaster: an observational study

Purpose Stable iodine prophylaxis helps prevent childhood thyroid cancer in nuclear emergencies; however, there is limited information on its effect on thyroid function. This study aimed to examine thyroid function and autoimmunity among children and adolescents that took stable iodine after the Fukushima Nuclear Disaster. Methods For this observational study, data were obtained from children and adolescents that underwent thyroid cancer screening at Hirata Central Hospital from April 2012 to March 2018. Participant characteristics, including possible hypothyroidism and hyperthyroidism, were compared between the prophylaxis and no-prophylaxis groups. Multivariable logistic regression models were used to assess for possible hypothyroidism, autoantibodies positive, and hyperthyroidism. Results A total of 1,225 participants with stable iodine prophylaxis and 3,946 without prophylaxis were enrolled. Of those participants, blood samples were available for 144 and 1,201 participants in the prophylaxis and no-prophylaxis groups, respectively. There were 17 (11.8%) and 146 cases (12.2%) of possible hypothyroidism or autoantibodies positive cases in the prophylaxis and no-prophylaxis groups, respectively, and there were no cases and 3 cases (0.2%) of possible hyperthyroidism in those two groups, respectively. Multivariable analysis for possible hypothyroidism revealed no association between stable iodine intake and possible hypothyroidism or autoantibodies positive [odds ratio 0.716 (95% confidence interval 0.399–1.284)] (p = 0.262). We did not perform multivariable analysis for hyperthyroidism due to the limited number of cases. Conclusion Significant adverse effects of stable iodine intake on thyroid function were not observed among children and adolescents 7 years after the Fukushima Nuclear Disaster.

Misdiagnosis of Paraganglioma by 123I-mIBG Without Stable Iodine Blockade of Thyroidal Radioiodine Uptake

Iodine-123/iodine-131 (123I/131I)-metaiodobenzylguanidine (mIBG) scan is an established tool for the localization and treatment of neuroendocrine tumors such as paragangliomas (PGL). To minimize thyroid irradiation by the radioactive iodine in the mIBG preparation, blockade of thyroidal iodine uptake with high doses of stable iodine used to be given routinely as part of all mIBG protocols. As 123I is now more frequently utilized than 131I, concern about thyroid radiation has lessened and thyroid blockade is often considered unnecessary. However, in certain situations, the lack of thyroid blockade can significantly impact treatment decisions. This report describes 2 patients who had mediastinal masses incidentally discovered on CT scans, and on further evaluation were found to have symptoms suggesting catecholamine excess with mildly elevated plasma normetanephrine levels. 123I-mIBG scans were performed without thyroid blockade, which demonstrated accumulation of tracer in the masses that were therefore deemed positive for PGL. Both patients underwent surgical resection of the masses with their surgical pathology revealing ectopic thyroid tissue (ETT). These cases illustrate that if appropriate thyroid blockade is not performed, ETT concentrating radioiodine from mIBG can lead to falsely positive mIBG scans and unnecessary surgical procedures. We conclude that in the setting of a mass suspicious for PGL in a location potentially representing ETT, such as the mediastinum, thyroid blockade should be employed for mIBG protocols to avoid false positive scans caused by ETT.

Social uncertainties related to stable iodine intake in a nuclear emergency

Intake of stable iodine intake is considered as an effective countermeasure for reducing the risk of thyroid cancer in an eventual release of radioactive iodine following nuclear accident. However, there are a number of value and social uncertainties that are likely to impact on accident management. These include differences in public response as well as decisions made by emergency management actors during an actual incident. In order to explore these sources of uncertainty, this paper explored social uncertainties related to the potential administration of stable iodine. First, public understanding and compliance with the advice of authorities was studied by surveys, showing that less than half of the public knew when iodine tablets should be taken, or understood their protective role. There were also country specific differences in the level of expected compliance with authorities’ advice. Second, social uncertainties were identified through observations of emergency exercises; these were revealed to be mainly related to timing, public response, communication, effectiveness, cross-border issues and first responders. Third, studies on factors influencing communication about stable iodine were carried out and showed that public understanding and compliance with advice could be improved by communicating numerical and narrative information. Overall, the results indicate that enhanced focus on social uncertainties during the preparedness phase may improve the effectiveness of stable iodine administration in case of an emergency.

Biological consequences of the spatial-differentiated level of the 131I accumulation in sheep thyroid after Chernobyl accident

&lt;p&gt;The aim of this work is to study the &lt;sup&gt;131&lt;/sup&gt;I biological effects on sheep at different concentrations of stable iodine in the diet. The problem of the absorbed dose estimation in the sheep thyroid gland (TG) after a radiation accident at the Chernobyl NPP in the conditions of natural micronutrient deficiency is considered. To determine the &lt;sup&gt;131&lt;/sup&gt;I critical dose in the sheep TG, leading to its dysfunction and subsequent destruction, complex laboratory studies were performed to refine the compartmental model parameters, based on reliable experimental and theoretical data. Modern technologies are used to model the TG area. The solution of the radiation transport equation is performed by the Monte Carlo technique, which takes into account both the &amp;#947; - and &amp;#946;-radiation of the &lt;sup&gt;131&lt;/sup&gt;I immanent source and the contribution of all secondary radiations.&lt;/p&gt;&lt;p&gt;The studies were carried out on 64 sheep, divided into 10 groups based on the general clinical condition and body weight. The first 5 groups included animals from the Gomel region (32 sheep, iodine content in the daily diet was 0.08 mg/kg ), in the 6&amp;#8211;10th groups (32 sheep; 0.43 mg/kg ) &amp;#8211; from the Vladimir region. Tests for iodine content in feed and water were performed in the Belarusian Institute of Experimental Veterinary Medicine, Minsk, 1989). For sheep 1&amp;#8211;3rd&amp;#160; , 6&amp;#8211;8th&amp;#160; groups (9 sheep in the group) once peroral the &lt;sup&gt;131&lt;/sup&gt;I was injected with activity: for the 1st&amp;#160; and 6th &amp;#160;groups &amp;#160;3 &amp;#181;Ci, for the 2nd&amp;#160; and 7th 15 &amp;#181;Ci, from the 3rd&amp;#160; and 8th&amp;#160; &amp;#8211; 72 &amp;#181;Ci&amp;#160; per capita. The surviving sheep were vaccinated against Rift Valley fever and then exposed to infection with an epizootic strain of the virus of this disease.&lt;/p&gt;&lt;p&gt;The main theoretical result is the conversion factor of the &lt;sup&gt;131&lt;/sup&gt;I activity to the average dose rate in thyroid. The main practical result is the evaluation of the lower limit of absorbed dose in the TG (~ 300 Gy), which leads to its destruction. Animals with a reduced content of stable iodine in the diet were characterized by an increased number of cells in venous blood, reduced levels of thyroxine in the serum, altered structure and functional activity of the thyroid and liver. In animals with low levels of iodine nutrition, a large capture of the isotope by the TG was noted, which provided larger (2&amp;#8211;5 times) doses. In sheep with iodine deficiency, a decrease in the number of leukocytes, thyroxine levels; survival is reduced. After the &lt;sup&gt;131&lt;/sup&gt;I intake, sheep developed a radiation-induced immunodeficiency, but the main mechanisms of the infectious process in animals remained: post-vaccination reactions proceeded without complications, were characterized by antibody formation and immune development.&lt;/p&gt;

Diagnostic possibilities for autoimmune thyroiditis using non-invasive determination of intrathyroid iodine concentration in children

Sixty-seven children (55 girls and 12 boys) aged 5-16 years were examined. Autoimmune thyroiditis (AT) was diagnosed in 28 and diffuse nontoxic goiter (DNG) in 39. The diseases were diagnosed on the basis of case history, results of examination and palpation of the thyroid, ultrasonic findings, presence of antibodies to thyroglobulin (in AT) or their absence (in DNG), and the microsomal fraction detected by enzyme immunoassay using Boehringer Mannheim kits. AT diagnosis was confirmed cytomorphologically in all patients. Intrathyroid stable iodine (ISI) was measured by a Russian noninvasive x-ray fluorescent analyzer. ISI concentration was notably decreased in children with autoimmune thyroiditis confirmed by cytomorphological methods: below the threshold level of the method in 46%) cases and 120±10 mcg/g in 54%). This confirms a high informative value of the proposed method in this disease. Measurements of ISI in children with enlarged thyroid helps differentiate the hypertrophic form of AT from DNG: ISI concentration under 200 mcg/g is characteristic of AT, while in DNG the concentration of ISI in Moscow children is 500±40 mcg/g (M±m).