Four days after fish caught were found to be contaminated with high levels of radioactive iodine, the government on Tuesday set the legal standard for iodine levels in seafood at the same level as vegetables of 2,000 becquerels per kilogram.
Four days after fish caught were found to be contaminated with high levels of radioactive iodine, the government on Tuesday set the legal standard for iodine levels in seafood at the same level as vegetables of 2,000 becquerels per kilogram.
Japanese sand lance caught on Friday by members of the Hirakata fishing cooperative in Kita-Ibaraki had levels of iodine of 4,080 becquerels per kilogram.
Officials of the Ministry of Agriculture, Forestry and Fisheries plan to ask Ibaraki Prefecture to stop shipments of sand lance under the Law on Special Measures Concerning Nuclear Emergency Preparedness. It would be the first time such a ban has been placed on seafood.
Another fishing cooperative in Otsu, Kita-Ibaraki, caught sand lance on Monday that had levels of radioactive cesium of 526 becquerels per kilogram, above the legal standard of 500 becquerels.
Officials of the Fisheries Agency asked Ibaraki prefectural government officials on Tuesday to halt fishing for sand lance. Fishing cooperatives throughout Ibaraki also decided on Tuesday to stop fishing for the small fish for the time being.
Legal standards for iodine in seafood had not been established because of the short half-life of eight days and the dispersion of iodine in seawater.
However, that changed after fish caught about 70 kilometers south of the crippled Fukushima No. 1 nuclear power plant were found to have high levels of iodine.
Fish caught near waters off Chiba Prefecture have also been tested a number of times, but none have exceeded established standards.
Ibaraki prefectural government officials approve the fishing of sand lance in designated waters by fishing cooperatives. The fisheries ministry will conduct detailed studies in those waters to determine which areas will be subject to the fishing ban.
The fisheries and health ministries had not until now instructed prefectural governments to conduct tests of seafood for radiation contamination.
Fishing cooperatives in Ibaraki Prefecture had asked a private-sector agency to test the fish caught.
Fisheries ministry officials will ask the Fisheries Research Agency to retest the fish.
Ministry officials also plan to expand the testing range for fish to include Tokyo, Kanagawa and Chiba prefectures as well as increase the frequency of the tests.
If other types of fish are found to have contamination levels exceeding established standards, the ministry plans to implement similar fishing bans.
According to officials of the Fisheries Agency, Ibaraki Prefecture accounted for 7 percent of sand lance caught in Japan in 2008. Even mature sand lance only grow to about 20 centimeters, so experts have pointed to the dangers of radiation becoming concentrated in larger fish that feed on the sand lance.
Sand lance also swim near the surface, unlike bottom feeders that were believed to be more prone to the effects of radioactive materials.
According to experts contacted by fisheries ministry officials, the sand lance may have become contaminated by seawater near the surface when the fish were caught in nets.
Ministry officials will also ask experts to reanalyze whether radioactive materials can become concentrated within fish because of the high figures found in the sand lance.
Kunikazu Noguchi, an expert on radiation protection at Nihon University, said, "There is the possibility that other small fish have also been contaminated. Larger fish that feed on such small fish could also become contaminated in the future."
He added that although half of the cesium ingested by fish is discharged as waste in about 50 days, the fact that the fish in the ocean are continuously exposed to radiation in seawater leaves open the possibility of further contamination of fish at high levels.
Noguchi said he was surprised at the high levels of iodine detected in the sand lance.
He added that a considerable amount of radioactive materials attach to seaweed after about a week to 10 days so seaweed in waters where radiation contamination has been confirmed should also be checked for contamination.
Noguchi also said that contamination by strontium was of concern because it can take 18 years for half of it to be discharged as waste matter from humans and because it can be accumulated in the human body due to characteristics similar to calcium.