Sand worms from waters off Iwaki have been detected to contain cesium. (Photo: Stock File/FIS)
Radioactive cesium entering food chain in waters off Iwaki
Friday, March 23, 2012, 15:30 (GMT + 9)
Some organisms in waters off Iwaki in Fukushima Prefecture have been found to carry amounts of radioactive cesium exceeding the government’s provisional limit of 500 Bq per kg. The discovery is helpful to understand how radioactive substances from the crippled Fukushima nuclear complex are moving along the food chain, according to a team of researchers.
Takashi Ishimaru, professor at Tokyo University of Marine Science and Technology, and his team extracted samples of four kinds of submarine organisms including sand worms from waters about 10 km from Iwaki and measured them for radiation in July 2011. They detected 854 Bq of cesium per kg in Echinocardium cordatum, the sea potato, and 471 Bq per kg of cesium in sand worms.
After doing similar research in the same area in October of last year, the team found 582 Bq of cesium per kg in Echinocardium cordatum and 328 Bq of cesium per kg in sand worms, which constitute prey for deep-sea fish such as flounder, Mainichi Daily News reports.
The research results were revealed in Tokyo this week.
The Fukushima Prefectural Federation of Fisheries Cooperative Associations, which includes six local fisheries cooperative associations, has voluntarily stopped fishing since the eruption of the crisis at the Fukushima No 1 Nuclear Power Plant.
Even so, fishery products from Japan exported to South Korea have appeared to be contaminated with radioactive materials with increased frequency. However, South Korea has no immediate plans to ban these imports because their radiation levels are far below safety limits, the Yonhap News Agency reports.
"The frequency of radiation detection appears to be rising as two reactors at the Fukushima plant are currently leaking radiation," an unidentified inspection official at the Animal, Plant, Fisheries Quarantine and Inspection Agency said, Kyodo reports. "But there has not yet been any case where Japanese fisheries products have been banned, as the level of cesium found in the products is still far below the international standard.”
The highest level of radiation detected in such products this year is 6.24 Bq, or about 1.7 per cent of the maximum limit of 370 Bq.
- 'Harmless' radiation found off Japanese coast
By Natalia Real