Evaluation of the results
Since previous epidemiological studies* indicate no significant health effects at doses ≤100 mSv, we concluded that radiation doses estimated so far are unlikely to cause adverse effects on health, although this conclusion is based on external exposure doses estimated only for the first four months following the accident.
* Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation; UNSCEAR 2008 Report to the General Assembly, Vol. 2 (Japanese-language version); National Institute of Radiological Sciences
Results of the Examination on the representativeness of dose distribution
In FY2015, a comparison was made between estimated doses for people selected at random from among those who had not responded to the Basic Survey (about 3,000 people) and estimated doses for people who had responded to the Basic Survey earlier in the same districts. As a result, it was confirmed that dose levels were almost the same for both groups and that the dose distribution compiled and publicized so far well represents the situation in the prefecture as a whole.
Significance of the survey
By aggregating the doses obtained from the Basic Survey, it was possible to ascertain the level of exposure of the entire population of the prefecture due to the accident, and to provide scientific evidence as to whether or not the level of radiation was high enough to cause direct health effects.
Outline of the Basic Survey
In consideration of radiation from the accident at TEPCO's Fukushima Daiichi NPS, caused by the Great East Japan Earthquake, the survey commenced with the aim of estimating external exposure doses of Fukushima residents based on self-reported location and activites, informing them of the results thereof, and linking such data to the improvement and maintenance of their health into the future.
Within Fukushima Prefecture
- Those who were registered as residents in Fukushima Prefecture between March 11 and July 1, 2011
Outside Fukushima Prefecture
- Those who lived in the prefecture between March 11 and July 1, 2011, but whose resident registration was outside the prefecture
- Those who lived outside the prefecture and commuted to work or school in the prefecture between March 11 and July 1, 2011
- Those who temporarily stayed in the prefecture between March 11 and March 25, 2011
For those who fall into categories 1 to 3 above, questionnaires sent upon their request.
Self-administered. Estimated doses will be sent to each individual who has returned the questionnaire response. There are two types of questionnaires as follows.
|Detailed Version||Those who changed their behavior patterns (i.e., changing residences, schools, or workplaces due to evacuation) more than twice in the four months after the earthquake, or could hardly determine their exact behaviors.|
|Simplified Version||Only for those who changed their behavior patterns (i.e., changing residences, schools, or workplaces due to evacuation) only once or less in the four months after the earthquake.|