Fukushima Fish Still Radioactive

the_newsbeagle writes "Bottom-dwelling fish that live near the wrecked Fukushima Dai-ichi nuclear power plant still show elevated radiation levels 19 months after the accident — and those radiation levels are not declining. Researcher Ken Buesseler says this indicates the seafloor sediments are contaminated (abstract), and will remain so for decades. He said, 'I was struck by how [the radiation levels] really haven’t changed over the last year. Since cesium doesn't bioaccumulate to a significant degree, and in fact is lost when fish move to a less contaminated area, this implies that the cesium source is still there'"

Absolute numbers?

[gman003]

I read both articles and the abstract, and couldn't find any actual numbers for how radioactive the fish are. And what I did find only made me want that answer more.

The only number that was being thrown around was "40%", in that 40% of fish caught in the Fukushima area exceed the limit for radiation, which is currently 100Bq/kg. But that's a rather low limit - before the accident, the limit was set to 500Bq/kg, but was tightened to reduce fears of contamination. And in the US (ever a paragon of strict food safety</sarcasm>), the limit is 1200Bq/kg.

So my question is, just how high *are* the radiation levels? Are the ones being rejected as unsafe doing so because the standards were tightened, or because they're genuinely highly radioactive?

Re:Fish

[mcgrew]

Not just fish. Ever hear of Project Censored? [illinoistimes.com]

A plume of toxic fallout floated to the U.S. after Japanâ(TM)s tragic Fukushima nuclear disaster on March 11, 2011. The U.S. Environmental Protection Agency found radiation levels in air, water and milk that were hundreds of times higher than normal across the United States. One month later, the EPA announced that radiation levels had declined, and they would cease testing. But after making a Freedom of Information Act request, journalist Lucas Hixson published emails revealing that on March 24, 2011, the task of collecting nuclear data had been handed off from the U.S. Nuclear Regulatory Commission to the Nuclear Energy Institute, a nuclear industry lobbying group. And in one study that got little attention, scientists Joseph Mangano and Jeanette Sherman found that in the period following the Fukushima meltdowns, 14,000 more deaths than average were reported in the U.S., mostly among infants. Later, Mangono and Sherman updated the number to 22,000.

Re:What was the baseline?

[cjameshuff]

Cesium doesn't bioaccumulate. It's not concentrated in any tissues, it's quickly excreted like sodium, potassium, etc. Strontium bioaccumulates, being treated like calcium and concentrating in bones, but at Fukushima it mostly stayed in the reactors...the stuff that escaped was mainly cesium and iodine (and the iodine has by now almost entirely decayed).

These fish are apparently maintaining a constant level by feeding in contaminated sediments that replace the cesium as fast as it is excreted. Predators will only have elevated levels while actively feeding on these bottom feeders. However, with a 30 year half life, there aren't many plausible sources for the cesium, it pretty clearly came from Fukushima. Given that a major tsunami had just happened, it's not surprising that there's a layer of sediment trapping the cesium. Possibly something could be done to free up the cesium so it can dilute more thoroughly, or cover it in uncontaminated sediments so bottom feeders don't get into it so much.