Experience of medical examination and health consultation for public exposed to neutrons caused by criticality incident in Japan

Introduction

A criticality incident occurred September 30th, in Tokaimura in Japan. Neutron radiation was emitted in a widespread area. In addition to three patients, who were exposed to high dose neutron radiation, people who were living around the incident plant (within 350 m) were urged to take shelter according to an evacuation order, and people who were living within 10 km‚ were also recommended to remain within their houses for three or four days.

We had an opportunity to examine and give advice to the people who feared the radiation exposure. The experience is reported.

Results

The criticality incident continued for nearly one day. From the next day after the end of criticality was declared, we started health examination. During the consecutivethree days, a total of 1852 people were examined. The complete blood count, including the hemogram or lymphocyte counts, and blood and urine chemistry were evaluated in all the patients. The survey of radiation contamination was done when patients requested. The history of the health condition and estimation of the radiated amount was evaluated by our members (physicians) in all the patients. Although many people complained of the fear of the after effects of radiation, the degree of fear was extremely strong in children and pregnant women. Regarding the results of blood and urine examination, there were no patients who had abnormalities that were thought to be caused by high amounts of radiation exposure, although there were several patients who had decreased lymphocyte counts.

Discussion and conclusions

Consultation only seems to be justified because, so far as we are informed officially (from the Japanese Agency of Science and Technology), the amount of radiation exposure was within the safe range. However, several patients who had decreased lymphocyte counts are recommended to receive repeated examination of the blood counts. Mental care and long-term follow-up may be necessary for people who are fearing the exposure and for children/pregnant woman.