Tokyo (CNN) -- The levels of radiation in ocean waters off Japan's embattled Fukushima Daiichi plant continue to skyrocket, the nation's nuclear safety agency said Thursday, with no clear sense of what's causing the spike or how to stop it.
The amount of radioactive iodine-131 isotope in the samples, taken Wednesday some 330 meters (361 yards) into the Pacific Ocean, has surged to 4,385 times above the regulatory limit. This tops the previous day's reading of 3,355 times above the standard -- and an exponential spike over the 104-times increase measured just last Friday.
Officials have downplayed the potential perils posed by this isotope, since it loses half of its radiation every eight days.
Yet amounts of the cesium-137 isotope -- which, by comparison, has a 30-year "half life" -- have also soared, with a Wednesday afternoon sample showing levels 527 times the standard.
"That's the one I am worried about," said Michael Friedlander, a U.S.-based nuclear engineer, explaining cesium might linger much longer in the ecosystem. "Plankton absorbs the cesium, the fish eat the plankton, the bigger fish eat smaller fish -- so every step you go up the food chain, the concentration of cesium gets higher."
Radiation levels in seawater off Japan plant spike to all-time highs - CNN.com
