The government has angrily taken issue with a May 23 report by the World Health Organization on overall levels of radiation exposure in Japan, accusing it of overestimating the problem.
The government has angrily taken issue with a May 23 report by the World Health Organization on overall levels of radiation exposure in Japan, accusing it of overestimating the problem.In its report, the WHO said residents living near the stricken Fukushima No. 1 nuclear power plant northeast of Tokyo were exposed to whole-body doses of between 10 and 50 millisieverts following the disaster last year.The estimates are higher than corresponding figures released in Japan, triggering a complaint from the government that the WHO had not done its homework properly.The WHO notified the government about a week earlier that it would release its own dose estimates on May 23. Officials in Tokyo were caught off-guard by the announcement."The WHO estimates deviate considerably from reality," said one anxious Japanese government source. "If those figures are taken at face value, that may spread disquiet and confusion among the Japanese public."Health vice minister Shinji Asonuma, who was visiting Geneva to attend a WHO general assembly, voiced his concern May 21 to WHO Director-General Margaret Chan. But that did not deter the U.N. organization from releasing its report two days later.This caused officials of relevant government ministries and agencies in Japan to scramble to compile a list of anticipated questions and answers for use by Cabinet members to explain the discrepancies.The WHO estimates were derived from data, released by the Japanese government last September or earlier, on concentrations of radioactive substances found in soil, air, foodstuffs, drinking water and seawater, and elsewhere.Researchers from the WHO, the Institute of Radiation Hygiene in Russia, the Federal Office of Radiation Protection in Germany and the Health Protection Agency of Britain handled different parts of the assessments. Their findings were then compiled by a WHO expert panel.Researchers from Japan's National Institute of Radiological Sciences and the National Institute of Public Health served on the expert panel.A couple of factors came into play to produce findings that startled Japanese officials. For example, residents living within a 20- to 30-kilometer radius of the Fukushima plant were assumed to have remained in the area for four months after the onset of the disaster, although, in reality, many of them evacuated earlier.The assessment of doses of internal exposure due to food consumption assumed that residents of Fukushima Prefecture only ate products produced in the prefecture. It also assumed that some contaminated foodstuffs slipped through shipment restrictions and were distributed."Because it is not possible to test each and every food product before going to market, the dataset (used to estimate the doses) includes a limited number of samples which are in excess of the food restriction levels and which were not eliminated by the enforcement measures," the WHO report says.The doses of internal exposure were found to be lower than 1 millisievert for more than 99 percent of the roughly 32,000 residents of Fukushima Prefecture who underwent health inspections by the prefectural government by the end of March. Those inspections only measured radioactive cesium, not radioactive iodine.The Fukushima prefectural government also evaluated the doses of external exposure for about 10,000 inhabitants of areas with high radiation based on records on the whereabouts of the individuals. That survey estimated the doses at less than 1 millisievert for nearly 60 percent of the subjects and more than 10 millisieverts for only 71 individuals."Overall, (the latest WHO figures) are overestimates," said Yoshio Hosoi, a professor of radiology at Hiroshima University's Research Institute for Radiation Biology and Medicine. "In particular, they have sharply overestimated the doses of external exposure and food-derived exposure," he said.But the Japanese government's System for Prediction of Environmental Emergency Dose Information (SPEEDI), which is designed to forecast the spread of radioactive substances, did produce larger thyroid gland dose estimates for 1-year-old infants in some districts of Namie, Fukushima Prefecture.In that case, the WHO estimates "probably mostly reflect reality," Hosoi said.The WHO began compiling the dose estimation report last summer. Its first draft, which appeared last November, startled one Japanese government official.The draft report estimated the whole-body doses for 1-year-old infants at 10-100 millisieverts in Namie and 1-10 millisieverts in Tokyo and Osaka.The thyroid gland dose estimates for 1-year-old infants were 300-1,000 millisieverts in Namie and elsewhere and 10-100 millisieverts in Tokyo and Osaka.Tokyo sent health ministry officials to the WHO headquarters and went through diplomatic channels to call for revisions."The figures are just impossibly high," a government official said at the time. "If they are released, that will not only arouse unnecessary anxiety among the Japanese public but also serve as negative publicity."Officials bent over backward to provide information on food regulations, the process of evacuation from areas around the nuclear plant, as well as dose inspection results and estimates available in Japan.The estimates underwent multiple amendments before the figures were released.Mikhail Balonov, a professor of radiological protection at the Institute of Radiation Hygiene in St. Petersburg, took part in the dose assessment.He said the estimates were revised as more data became available, adding that the final figures came to more accurately reflect the reality in Japan today.