Internal exposure risk due to radiocesium and the consuming behaviour of local foodstuffs among pregnant women in Minamisoma City near the Fukushima nuclear power plant: a retrospective observational study

OBJECTIVES: This study aimed to evaluate the internal cesium (Cs) level among pregnant women in Minamisoma City (the area straddling the evacuation zones) over a 5-year period after Japan's 2011 Fukushima nuclear accident and assess the status and transition of their food-acquiring preferences during this period. DESIGN: A retrospective observational study of a screening along with a questionnaire survey. SETTING: This study was conducted in an obstetrics and gynaecology service in Minamisoma City in Fukushima, Japan. PARTICIPANTS: Participants included pregnant women who applied for the voluntary internal radiation exposure screening programme. PRIMARY AND SECONDARY OUTCOME MEASURES: Internal radiation exposure was evaluated using the whole-body counter (WBC) in the screening programme. Data from a food acquisition preference questionnaire administered to the participants were analysed and compared across the 5-year period after adjusting for covariates. RESULTS: Overall, 804 screening programmes were conducted with 579 participants during the study period. All participants had internal contamination levels below the detection limit of the WBC unit (220 and 250 Bq/body for Cs-134 and Cs-137, respectively). Based on the most conservative assumption, their maximum annual effective doses by Cs-134 and Cs-137 together were estimated at 16 µSv/year. Contrary to limited internal contamination risks and counter-dose initiatives by the government, a considerable number of pregnant women were still concerned about consuming potentially contaminated local food products when purchasing them at supermarkets between 2012 (78.4%) and 2015 (75.0%). CONCLUSIONS: Health effects from post-accident internal radiation exposure were likely to be insignificant in pregnant women. National/local action is urgently needed to promote scientific understanding in pregnant women regarding limited internal exposure risks from local food products in the market. However, few mothers chose to participate in the internal radiation exposure screening programme, and thus, caution is required in interpreting the results of analyses