Several studies bear out his views. A fortnight after the disaster, the authorities screened the thyroids of 1,149 children exposed to radiation and found that the maximum equivalent thyroid dose was 35 millisieverts (mSv). This is much less than at Chernobyl. Researchers from Japan’s Hirosaki University followed up the study a few weeks later. Their findings, published recently, showed iodine-131 active in the thyroids of 46 out of 62 evacuees. The average dose was about 3.5mSv in adults and the equivalent of 4.2mSv in children—which is better than 100 times less than the average for Chernobyl evacuees, 490mSv.
According to a draft report of the Fukushima Health Management Survey Group, which is canvassing the prefecture’s 2m residents on their health problems, ultrasound examinations of 38,114 children in Fukushima have so far revealed no evidence of thyroid problems. However, because thyroid cancer takes time to appear, the survey will continue for three years.
Dr Yamashita says a questionnaire answered by 15,000 villagers (of the 30,000 who were evacuated from near the nuclear power plant) showed that in the four months after the disaster, almost all had an accumulated exposure of less than 10mSv. This suggests a rate far below the rate of 100mSv per year at which health problems are proven to emerge, he says.
His views on the relative safety of radiation exposure below 100mSv are controversial, especially in Fukushima. But it is supported by the Hiroshima-based Radiation Effects Research Council, an American-Japanese scientific body whose studies date back to 1947. At times, the government, media and scientists have issued a bewildering mixture of messages, some of which suggest that much lower levels could be dangerous—especially to children. Dr Yamashita has been given the disparaging moniker “Dr 100 millisievierts” for sticking to his guns, and he remains unrepentant. He notes that while nobody in Fukushima has died as a result of radiation, there were 761 victims of “disaster-related death”, especially old people uprooted from homes and hospital because of forced evacuation and other nuclear-related measures.
As in Chernobyl, he argues, the psychological trauma of evacuation, overlaid by the fear of radiation, poses the biggest health risk. According to the Fukushima health survey, 14.6% of almost 9,000 pregnant women who replied indicated some feelings of depression. As in Chernobyl, the empty bottles of sake outside temporary housing complexes are an indication that more such trouble may lie ahead. Yet Dr Yamashita says too little attention is being paid to the post-disaster trauma. There is a “complete shortage” of well-trained local staff to act as counsellors.
He is not willing to advocate a return to the radiated areas, though surveys after Chernobyl showed that those who stayed in contaminated areas coped better psychologically than those who were forced to leave. There is still too much mistrust and anger towards Tepco, operator of the plant, he says. And infrastructure, health facilities, jobs and land are still in disarray.
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