March 22, 2011
Levels of iodine-131 were 126.7 times higher than the limit set by the government and cesium-134 was 24.8 times higher, while cesium-137 was 16.5 times higher, according to a study conducted Monday by Tokyo Electric Power Co. on seawater collected about 100 meters from the crippled plant’s drainage pipes.
Japan’s Chief Cabinet Secretary Yukio Edano said there was no immediate cause for alarm but that a future ban on seafood from the area was a possibility. “It is not necessary at the moment," Edano told a news conference Tuesday morning. "But it is necessary to collect data from a wider range and firmly continue to have experts analyze them."
Japan has already put a ban on spinach and milk from the immediate area around Fukushima after elevated levels of radioactive iodine and cesium were discovered over the weekend. Government officials have been anxious to avoid public panic over food supplies and export commodities.
Ingestion through the food chain proved to be the principle form of damaging exposure to radiation at Chernobyl. Iodine-131 that landed on fields in the region was ingested by cows, which passed it through as milk that was ingested by people in the region. Iodine-131 migrates to the thyroid gland where gives heavy doses of radiation, especially in children whose thyroids are particularly active. Four thousand cases of thyroid cancer resulted, mostly among children, leading to 10 fatalities. All these events took place behind the Iron Curtain, however, and Soviet officials were completely unprepared. There was no distribution of iodine pills and no effort to monitor ingestion. Iodine-131 has a half-life of only eight days and disappeared entirely after two months, so the danger is short-lived.
Cesium 137 and 134 are bigger problems because they have longer half-lives and because they mimic sodium and potassium and can take up long-term residence in the body. Cs-134’s half-life is 3-1/4 years and Cs-137 is considered the worst danger, with a half-life of about 30 years. Strontium-90, which mimics calcium and has a half-life of 29 years, is the other fission by-product that is considered the worst long-term danger.
At this point the levels of all these elements are not a cause for alarm. But Japanese officials said they would be monitoring the dangers. "As part of our country’s nuclear power policy, it has been necessary to be able to monitor the level of radiation to ensure it was all right,” said Edano. "The public may have anxiety over the fact that the level has exceeded the standards . . . but I would like them to understand that these numbers are extremely conservative."â€¨
Read more about it at the Japan Times