Monday, April 4, 2011
MORE ON RADIATION IN FISH AND SHELLFISH
I blogged on March 27 about the likely risk of radiation contamination of fish and shellfish near the Fukushima power plant. That was over a week ago. It was also before we heard about the tons of radiation-contaminated water flowing into the sea near the Fukushima power plant. In fact, the latest numbers say about 7 tons of radiated water an hour is flowing into the sea from that crack in the pit at the damaged Reactor No. 2 (where ongoing efforts are now resorting to newspaper and sawdust to plug it). It was also before concerns about radiation in fish affected fresh fish sales in Tokyo, and before the media began to discuss it all over the world, including in the U.S.
And, it was before there were any reported findings of radiation in seafood near the Fukushima plant. The International Atomic Energy Agency has now reported that at the port of Choshi, in Chiba prefecture south of Fukushima, about 20% of the fish caught have been found to have elevated levels of caesium-137 (not high enough to be considered unsafe - yet).
Caesium-137? Isn't everyone talking about iodine-131? Well, yes. But most radioisotopes, including Iodine-131, have pretty short half lives (the time it takes for half the amount that initially enters the water to decay), measured in days or weeks. Testing may show elevated levels in surface seawater now (and I bet it's in lakes and rivers too) but it will get diluted, and soon just decay. In fact, the International Atomic Energy Agency said iodine-131 in seawater would “soon be of no concern.”
But other radioisotopes such as caseium-137 and stronium-90 can stick around for a long time - years, and even decades. I gather from the research on Chernobyl, that if it's in water bodies it's likely to sink down into the sediment and bioaccumulate (that is, build up) in the fish and shellfish in the area.
I wonder when we'll hear about the levels of caesium-137 found in seafood in rivers and lakes near Fukushima? I would guess, pretty soon.
By the way, I notice that my local store has stopped selling scallops imported from Japan.