Stable iodine distribution among children after the 2011 Fukushima nuclear disaster in Japan: An observational study

Abstract

Context: Intake of stable iodine helps prevent childhood thyroid cancer in nuclear emergencies, but there is limited case information. Objective: We identified the intake rate and the factors associated with no intake among children who did not take stable iodine after the Fukushima disaster. Design: Retrospective observational study. Setting: Data were obtained from thyroid cancer screenings performed from August through November 2017. Participants: Children in Miharu Town, Fukushima, Japan. Intervention: No intervention. Main Outcome Measures: We performed multilevel logistic regression analysis at the regional and individual levels. We qualitatively examined the reasons for no intake of stable iodine based on closed- and open-ended questions. Results: The rate of distribution was 94.9%, but the intake rate was only 63.5%. Intake was lower in those aged 0 to 2 years compared with those aged $3 years (OR, 0.21; 95% CI, 0.11 to 0.36). Parents' intake was positively associated with their children's intake (OR, 61.0; 95% CI, 37.9 to 102.9). The variance partition coefficient for regions was 0.021, suggesting that the intake of stable iodine was more likely affected by individual than by regional factors. Closed-ended questions showed that the main reason for avoiding intake was concern about safety. Open-ended questions for other reasons revealed issues related to the distribution method, information about the effects and adverse effects of iodine, and instructions for iodine intake. There were no symptomatic adverse effects claimed to the town. Conclusions: The distribution and consumption of stable iodine occurred in Miharu Town after the Fukushima disaster. To prepare for future nuclear emergencies, it is important to explain to both children and parents the need for intake of stable iodine, particularly among young children.