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Cesium in fish

Dear Reader,

I imagine since the horrible reactor accident in Japan that a lot of questions have arisen. One of these has been will fish be safe to eat ?

I suspect that some “experts” will make statements suggesting that the Fukuashima fish will either be safe/unsafe to eat (delete as appropriate to suit the political stance of the “expert”). But rather than just making or accepting a blanket statement as to the safety (or otherwise) of fish lets look at some of the evidence.

In one study Japanese cat fish (Silurus asotus Linnaeus) were placed in a big fish tank where the water had been spiked with 137Cs. This paper was written by M.A. Malek, M. Nakahara and R. Nakamura, Journal of Environmental Radioactivity, 2004, volume 77, pages 191 to 204.

To cut a long story short what happened was that the fish did absorb radioactivity. It is important to understand that just because a fish becomes radioactive it does not mean that a human would absorb any radioactivity from eating the fish. For examine 90Sr absorbs into the bones of the fish, as long as you do remove the bones before cooking the fish (and do not boil the bones into soup) then the 90Sr in the bones of a fish that you buy in the supermarket are unlikely to be ingested when you eat a fish dinner. 137Cs on the other hand is an isotope which goes into the edible part of the fish (the muscle tissue), so the cesium in the fish is a possible threat to the consumer (bad news).

The cat fish are fresh water fish, I have to confess I do not know much about fish but I reasoned that if the fish are concentrating potassium out of the water into their bodys then in the sea the higher concentrations of potassium may tend to block the absorption of cesium into the fish. But when I checked I. Antovic and N.M. Antovic, Journal of Environmental Radioactivity, 2011, volume 102, pages 713 to 717 it stated that for mullet that does cesium does concentrate in sea fish. I have not worked out quite how the cesium gets into the fish.

So attention needs to be paid to the cesium levels in the fish near Japan.


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