Relationship between haematological data and radiation doses of TEPCO workers before and after the FDNNP accident

We evaluated the correlation between radiation dose and the medical examination data of Tokyo Electric Power Company Holdings, Inc (TEPCO) employees working during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011. This study included 2164 male TEPCO workers who received periodic medical examinations from March 2006 to January 2013. First, we conducted log-linear regression analyses using the haematological data of 585 emergency workers and confounding factors to examine the effect of internal radiation exposure in March 2011. Since external radiation exposure was a major influence, we then evaluated the correlation between both internal and external radiation dose and the haematological data of 1801 emergency workers and confounding factors before and after the accident. Among 585 workers, internal radiation exposure in March 2011 alone was mainly due to thyroid doses (0.1-10 Gy) but not to bone marrow (BM) doses (0.01-1 mGy). Compared to before and after the accident, we found that the levels of monocytes, eosinophils (Eos) and basophils increased slightly, whereas the frequency of smoking and alcohol consumption decreased substantially. External dose exposure was positively correlated with haemoglobin (Hb), red blood cell and Eos but negatively correlated with age, haematocrit and frequency of alcohol consumption. Among these variables, Hb exhibited the strongest correlation with external dose. Regarding the correlation with Hb, although there is a possibility that confounding factors other than exposure were not evaluated, our findings on emergency workers can serve as a reference for the evaluation of health conditions during the emergency period of future nuclear-related accidents.