FUKUSHIMA--The Fukushima prefectural government plans to monitor health effects from radiation leaking from the Fukushima No. 1 nuclear power plant in a program that could follow some residents for up to 30 years.
FUKUSHIMA--The Fukushima prefectural government plans to monitor health effects from radiation leaking from the Fukushima No. 1 nuclear power plant in a program that could follow some residents for up to 30 years.
The study will be an unprecedented one in terms of length and number of people covered. But because it will be impossible to conduct thorough health checks on all 2 million residents of Fukushima, a two-step plan is being considered.
A preliminary study will begin in early July on a small sample of residents from areas that have had high radiation levels in the air.
The preliminary study will be used to prepare for the wider study and will also be designed to alleviate the health concerns of Fukushima residents.
Details of the preliminary study are expected to be decided on at a meeting June 18 of Fukushima prefectural government officials, officials of the relevant central government ministries as well as experts in radiation medicine.
The prefectural government plans to hold meetings before the start of the study to explain to residents what will be done and address other concerns they may have.
Under the proposal for the preliminary study, about 100 residents from such municipalities as Iitate and Namie that have had high radiation readings will be selected as a sample group.
Those selected will undergo thorough testing for internal radiation contamination, including testing with a whole body counter as well as checks of the thyroid gland where radioactive iodine can readily accumulate. Urine samples will also be tested to determine if radioactive materials were ingested.
Various municipal governments will be asked to choose the subjects, including children, but the total number of people selected could exceed 100.
The residents will be asked to fill out a detailed questionnaire showing the location and how much time they spent indoors, outdoors or in cars over about a two-week period from March 11.
Experts will use that information to estimate radiation levels the individual may have been exposed to based on the levels in the air for those times.
The estimated radiation levels will be compared with actual radiation levels detected during the in-depth measuring stage.
The selected residents will also be asked how much milk they drank from cows raised on family farms and how much water from nearby wells. Women will be asked if they are pregnant or breast-fed their babies.
The prefectural government plans to complete the preliminary study by the end of July and begin the actual study from autumn.
All Fukushima residents will receive questionnaires through the mail to record what they did and where they were over the two-week period from March 11. Estimates of radiation exposure levels will be calculated in a similar fashion to the preliminary study.
Because thorough radiation monitoring of all Fukushima residents would be impossible, only those found to have comparatively high estimated radiation exposure levels will actually undergo monitoring that includes blood and urine tests.
The data will be stored for at least 30 years at a database created by the Fukushima Medical University to conduct follow-up health checks on residents found to have high exposure levels.
Because residents will be asked to recall what they did over a two-week period from about three months ago, researchers will be racing against time to accumulate accurate records that can help make valid estimates.
Hydrogen explosions at a number of reactors at the Fukushima No. 1 plant in the first few days after the nuclear accident led to radioactive materials being spewed over a wide area.
That means the amount of time a resident spent outdoors during that time will greatly influence his or her radiation exposure level.
Despite the scale of the proposed study, it may not be easy to clearly determine what, if any, health effects may occur due to the radiation from the Fukushima plant.
It has generally been thought that health effects will only arise if an individual is exposed to more than 100 millisieverts of radiation. However, the general opinion of experts is that the average Fukushima resident was likely exposed to, at most, several dozen millisieverts of radiation.
Although that is much higher than the 2.4 millisieverts per year of natural radiation in the air, it is not at a level in which health effects have been confirmed in past studies.
"At such low levels of radiation exposure, it is very conceivable than health effects from smoking or the stress of evacuation could be greater than radiation exposure," said Toshiteru Okubo, chairman of the Radiation Effects Research Foundation.
However, the experience of hibakusha atomic-bomb survivors in Hiroshima and Nagasaki also indicates that it will take decades before health effects from radiation exposure, such as an increase in cancer, become obvious.
The Fukushima study will go beyond any that has been conducted on hibakusha in Hiroshima and Nagasaki because it will include measurement of internal contamination levels.
(This article was written by Yuri Oiwa, Yasufumi Kado and Yoshinori Hayashi.)