6 Mai 2016
May 6, 2016
By MASAKAZU HONDA/ Staff Writer
A coalition of 30 private groups is digging deeper into radiation contamination from the 2011 Fukushima nuclear disaster to address persistent concerns from the public around Japan.
The coalition’s website, titled the East Japan Soil Measurement Project, shows radiation levels in soil samples taken from more than 1,900 sites in Tokyo and 16 prefectures, from northeastern Japan to the Pacific side of the central Japan.
The project was started partly because parents were concerned that local governments were using only airborne radiation levels to determine if outdoor areas were safe for children.
While radioactive contamination in the air decreases as time passes, that is not necessarily the case with radioactive substances in the ground.
The group’s survey of land contamination has found “hot spots,” where levels are significantly higher than in the surrounding neighborhoods, five years after the disaster unfolded at the Fukushima No. 1 nuclear plant.
The radiation levels in some of those areas are comparable to those at nuclear reactor buildings and medical institutions that provide radiation therapy, where public access is restricted because annual radiation doses can exceed 5 millisieverts.
Three citizens groups, including the nonprofit organization Fukushima 30-Year Project, created the website after forming an extensive network of private entities in October last year.
The groups conduct the measurements in a unified manner. About 1,000 cubic centimeters of soil samples are taken by digging 5 cm deep in the ground in the shape of a 10-cm-by-20-cm block in residential areas and districts that ordinary citizens are allowed to enter.
Extreme anomalies in the radiation measurements are not posted on the site because the purpose of the project is to show average contamination in local communities.
“We want to prevent viewers from misunderstanding the pollution level of a given community just because of isolated cases of high numbers,” said Hidetake Ishimaru, head of the coalition’s secretariat. “Viewers can get tips on how to avoid risks in daily life by comparing figures that were measured in a standardized manner.”
The highest reading so far was 135,000 becquerels of radioactive cesium detected in a forest near a home in the Hiso district of Iitate village, northwest of the embattled Fukushima No. 1 nuclear power plant.
The soil sample showed 111,028 becquerels of cesium-137 and 23,920 becquerels of cesium-134.
Radioactivity readings at many observation spots in Shizuoka Prefecture, which is far from the nuclear plant, were below the lowest detectable level.
But the survey this year still found sites in the Kanto region, south of the Tohoku region where the Fukushima plant is located, with readings exceeding 10,000 becquerels.
Save Child Iwate, a group in Iwate Prefecture, was the first of the 30 collaborating private organizations to take measurements in the soil.
Save Child Iwate started measuring radiation doses in the atmosphere and radioactivity in the soil throughout the prefecture in spring 2012. Many of the sites were at schools and parks. It has measured doses at 316 spots and publicized the results.
Kazuhiro Sugawara, a 39-year-old staff member of Save Child Iwate’s secretariat, said the group began measuring radioactivity in soil after local governments had insisted that it was safe to let children play outdoors.
Local officials cited low radiation doses in the air in their safety assurances.
But the group remained skeptical because the evacuation order for residents from the 1986 Chernobyl nuclear disaster was issued in part based on the extent of ground contamination.
Sugawara’s daughter was 10 years old and attending an elementary school in Iwate Prefecture when the disaster started at the Fukushima nuclear plant. Like other parents in the area, Sugawara was most concerned about the safety of the children.
“We cannot feel safe without data on soil contamination because children play with earth, wipe the mouths with their dirty hands and inhale dirt blown up by wind, exposing themselves to the risk of internal radiation exposure,” Sugawara said about why he undertook the project. “If local officials would not bother to measure soil contamination, we decided to do so on our own.”
The highest land contamination figure Save Child Iwate recorded came from samples from private property in Kanegasaki in the prefecture in June 2012.
At that spot, the radiation level in the air was 0.24 microsieverts per hour, while radioactivity in the soil sample exceeded 4,500 becquerels.
The coalition accepts sample soils sent by concerned citizens for free measurements using funds provided by businesses and donations from the public.
It currently lacks sufficient data from Niigata, Tochigi and Gunma prefectures.
“Part of the reason we cannot enlist cooperation from groups in the three prefectures, where agriculture is thriving, is that they fear possible negative publicity,” Ishimaru said.
The coalition plans to hold workshops for citizens around the nation on how to gather samples to broaden support for the endeavor.
Tetsuji Imanaka, a researcher with Kyoto University’s Research Reactor Institute who has been monitoring land contamination in Fukushima Prefecture and elsewhere, stressed the importance of gaining data from soil.
“Since numbers on land contamination are basic data needed to study the scope of pollution in a given region, detailed surveys are necessary,” he said. “Ideally, local officials should do the task. I am hoping that the coalition will play a significant role.”