Cancer risk linked to radiation levels in fish species after Fukushima 福島事故により放射能汚染された魚介類により、がんにかかる危険性が増えた。

(Source) http://www.straight.com/life/497651/cancer-risk-linked-radiation-levels-fish-species-after-fukushima


Two-and-a-half years after Fukushima, many fish species still have highly elevated amounts of radioactive cesium from the stricken plant, including species that Japan exports to Canada, according to the Japanese Fisheries Agency’s tests on fish catches.



And Japanese fish and seafood exports to Canada have grown significantly since Fukushima, with $24 million in exports in 2012, up 20 percent from $20 million in 2010, according to Statistics Canada data.
In July this year, a sea bass caught in Japan had 1,000 becquerels per kilogram of radioactive cesium—10 times Japan’s ceiling of 100 becquerels per kilo in food. It was the second-highest amount found in a sea bass since the disaster occurred.
And in February, a greenling in the harbour of the Fukushima plant had a record 740,000 becquerels per kilo of cesium—7,400 times Japan’s ceiling. Two in five fish tested in July had detectable levels of cesium 134 or cesium 137, radioactive isotopes released from Fukushima.
On average, fish in the 33,000 tests since March 2011 had 18 becquerels per kilo of cesium. In March and April 2011, fish also had 65 becquerels per kilo of iodine 131. (The Straight didn’t count in these averages any fish caught in Fukushima prefecture, where most species are banned from the market.)
Fish caught far out in the Pacific had an average of two becquerels of cesium per kilo.
The Straight used these levels to determine how much radiation the public has been exposed to in Japan and elsewhere, based on fishery data from the United Nations’ Food and Agriculture Organization.
The average radiation levels are below Japan’s ceiling and Health Canada’s much higher ceiling of 1,000 becquerels per kilo for cesium and iodine 131.
But the radiation detected can still cause cancer, according to the U.S. Environmental Protection Agency’s cancer-risk formula, a leading international standard for forecasting cancer risks from radiation.
What’s more, the EPA formula underestimates cancer impacts because it doesn’t fully include all research on radiation impacts, in the estimate of Daniel Hirsch, a UC Santa Cruz nuclear expert.
(Also according to Hirsch, Health Canada uses a less accepted cancer-risk formula that underestimates the dangers even more.)
Hirsch helped preside over a study of nuclear-power workers in the 1990s that found cancer rates at least six to eight times higher than predicted by official formulas.