Effects of external radiation dose on pediatric peripheral blood components after the Great East Japan Earthquake: Fukushima Health Management Survey

The Great East Japan Earthquake (GEJE) caused an accident at the Fukushima Daiichi Nuclear Power Plant, resulting in widespread dispersion of radioactive materials across the Fukushima Prefecture. We aimed to analyze the effects of external radiation exposure after the GEJE on peripheral blood components in children living in the evacuation area. We analyzed 27,844 children aged ≤ 15 years, including residents of evacuation areas and infants aged < 1 year born to parents residing in these areas. All participants underwent comprehensive health checks between 2011 and 2017, with available data on effective radiation dose due to external exposure (EDEE) during the first 4 months post-GEJE. Participants were categorized by age as: <1, 1–4, 5–10, and 11–15 years. The mean (standard deviation) of EDEE was 0.8 (0.7) mSv, ranging from 0.1 to 8.8 mSv in males and 0.1–8.9 mSv in females. When stratified into groups with mean EDEE < 1 mSv and ≥ 1 mSv, peripheral blood parameters remained within reference intervals, and no significant changes over time were observed across age groups. Additionally, the upper and lower 5% of white blood cell counts did not correlate with EDEE, including neutrophils and lymphocytes.