White Blood Cell, Neutrophil, and Lymphocyte Counts in Individuals in the Evacuation Zone Designated by the Government After the Fukushima Daiichi Nuclear Power Plant accident: The Fukushima Health Management Survey

BACKGROUND: Lymphocytes are susceptible to damage from radiation, and the white blood cell (WBC) count, including counts of neutrophils and lymphocytes, is a useful method of dosimetry. According to the basic survey of the Fukushima Health Management Survey (FHMS), among 13 localities where evacuation was recommended, Iitate and Namie had more individuals with external radiation exposure of more than 5 mSv than the other evacuation areas. We analyzed whether or not WBC, neutrophil, and lymphocyte counts decreased after the disaster. METHODS: The subjects of this study were 45 278 men and women aged 20 to 99 years (18 953 men and 26 325 women; mean age 56 years) in the evacuation zone who participated in the Comprehensive Health Check (CHC) from June 2011 to the end of March 2012. RESULTS: Significant differences were detected in the mean values of WBC, neutrophil, and lymphocyte counts, and for the proportion of individuals under the minimum standard for WBC and neutrophil counts, among the 13 localities. However, the distribution of individuals at each 200-cell/µL increment in lymphocyte count were similar in these areas, and the WBC, neutrophil, and lymphocyte counts did not decrease in Iitate or Namie specifically. CONCLUSIONS: No marked effects of radiation exposure on the distribution of WBC counts, including neutrophil and lymphocyte counts were detected within one year after the disaster in the evacuation zone.