Masaharu Tsubokura1, Shuhei Nomura2, Hajime Watanobe3, Yoshitaka Nishikawa4, Chiaki Suzuki5, Sae Ochi6, Claire Leppold7, Hirokatsu Kinoshita8, Shigeaki Kato9, Yasutoshi Saito1. 1. 1 Department of Internal Medicine, Hirata Central Hospital , Hirata, Fukushima, Japan . 2. 2 Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London , London, United Kingdom . 3. 3 Wako Fukushikai, Wako, Saitama, Japan . 4. 4 Department of Health Informatics, School of Public Health, Kyoto University , Kyoto, Japan . 5. 5 Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University , Kyoto, Japan . 6. 6 Department of Internal Medicine, Soma Central Hospital , Soma, Fukushima, Japan . 7. 7 Department of Research, Minamisoma Municipal General Hospital , Minamisoma, Fukushima, Japan . 8. 8 The Institute for Humanistic Studies, Kamakura Women's University, Kamakura, Kanagawa, Japan . 9. 9 Research Institute of Innovative Medicine, Tokiwa Foundation, Iwaki, Fukushima, Japan .
Abstract
BACKGROUND: Iodine deficiency is an important modifier of the risk of thyroid cancer following irradiation. However, little information is available on the prevalence of iodine deficiency in Fukushima and its surroundings after the Fukushima Daiichi nuclear power plant accident that occurred in March 2011. METHODS: In order to assess urinary iodine concentrations (UIC) and the prevalence of iodine deficiency and to elucidate any associations between demographic characteristics and UIC levels among children and adolescents aged ≤18 years at the time of the accident in Fukushima Prefecture and its surroundings, the data on voluntary UIC testing conducted by Hirata Central Hospital, Fukushima, were evaluated. RESULTS: A total of 4410 children and adolescents with a median age of 10 years at examination underwent UIC testing between October 2012 and October 2015. Calculated for all the participants, the median UIC level was 204 μg/L (range 25-21,100 μg/L). There were 133 (3.0%), 732 (16.6%), and 1472 (33.4%) participants with UIC levels of <50, <100, or ≥300 μg/L, respectively. Based on the World Health Organization criteria for nutritional iodine status, no participants were severely iodine deficient (<20 μg/L), but 16.6% of the population were mildly (50-100 μg/L) or moderately (20-50 μg/L) iodine deficient. While no significant difference in UIC was noted between those who did and did not increase dietary iodine intake after the accident (p = 0.93), there were significant differences by year (p < 0.01), school level (p < 0.001), and residential area at the time of the accident (p < 0.001). CONCLUSIONS: This study demonstrates that the children and adolescents examined had a sufficient amount of iodine during the period 1.5-4.5 years after the nuclear accident. In addition to the differences in the scale and the countermeasures undertaken between the Fukushima and Chernobyl accidents, differences in dietary iodine intake might have played an additional role in resulting in the reportedly different radiation doses to the thyroid between the two nuclear accidents.
BACKGROUND:Iodine deficiency is an important modifier of the risk of thyroid cancer following irradiation. However, little information is available on the prevalence of iodine deficiency in Fukushima and its surroundings after the Fukushima Daiichi nuclear power plant accident that occurred in March 2011. METHODS: In order to assess urinary iodine concentrations (UIC) and the prevalence of iodine deficiency and to elucidate any associations between demographic characteristics and UIC levels among children and adolescents aged ≤18 years at the time of the accident in Fukushima Prefecture and its surroundings, the data on voluntary UIC testing conducted by Hirata Central Hospital, Fukushima, were evaluated. RESULTS: A total of 4410 children and adolescents with a median age of 10 years at examination underwent UIC testing between October 2012 and October 2015. Calculated for all the participants, the median UIC level was 204 μg/L (range 25-21,100 μg/L). There were 133 (3.0%), 732 (16.6%), and 1472 (33.4%) participants with UIC levels of <50, <100, or ≥300 μg/L, respectively. Based on the World Health Organization criteria for nutritional iodine status, no participants were severely iodine deficient (<20 μg/L), but 16.6% of the population were mildly (50-100 μg/L) or moderately (20-50 μg/L) iodine deficient. While no significant difference in UIC was noted between those who did and did not increase dietary iodine intake after the accident (p = 0.93), there were significant differences by year (p < 0.01), school level (p < 0.001), and residential area at the time of the accident (p < 0.001). CONCLUSIONS: This study demonstrates that the children and adolescents examined had a sufficient amount of iodine during the period 1.5-4.5 years after the nuclear accident. In addition to the differences in the scale and the countermeasures undertaken between the Fukushima and Chernobyl accidents, differences in dietary iodine intake might have played an additional role in resulting in the reportedly different radiation doses to the thyroid between the two nuclear accidents.
Entities:
Keywords:
dietary intake; iodine deficiency; radiation exposure; thyroid cancer