[ RadSafe ] Cesium in Fukushima fish
bradkeck at me.com
Mon Oct 29 08:09:43 CDT 2012
The Science article is brief and available at the AAAS website or your local library. (There is not a distinction in the paper as to how much is 137Cs and how much is 134Cs - a bit disappointing in that regard, but ALI's are similar.)
if you look at this with a little more perspective, you would find that, even if all the fish in one's typical diet of 70 kg/year came only from demersal, near-Fukushima fish (let's say you are a fan of Fukushima halibut, for instance) and was at the Japanese limit of 100 Bq/kg, then you would be consuming a whopping 7,000 Bq of cesium per year - this translates to something about 13 mrem/y.
Given that our unavoidable radiation dose is on the order of 350 mrem/y, eating fish would seem to be more an academic or nutritional exercise than a toxicologic one.
I plan to visit Japan soon and I will be eating the halibut - I promise a tasty review!
Bradly D. Keck, PhD, CHP
On Oct 26, 2012, at 2:26 PM, Maury wrote:
> Thank you very much for the information you have added to this picture.
> Hope yuo have a pleasant Fall weekend,
> Maury&Dog [MaurySiskel maurysis at peoplepc.com]
> On 10/26/2012 12:03 PM, Lantzelot wrote:
>> The measured activities in the Baltic Sea may be an interesting comparison for "extreme" values.
>> Anti-nuclear groups often mention the Baltic Sea being the world's most radioactive sea, see for instance the following document with Cs-137 levels in fish from various seas measured during the 1990's: http://www.nonuclear.se/files/baltic-radioactive200612.pdf
>> As you can see from the first graph the activity is of the order of 20 Bq/kg fish, though near some sediment hot-spots fish with up to 200 Bq/kg have been found (there are inland fish in Sweden with much higher levels). The activity level of Cs-137 in the water is about 45 Bq/m3.
>> As a side note, the relatively high level is due to 80% from the Chernobyl accident. The rest is from atmospherical nuclear tests in the 1950-60's and from the Sellafield and La Hague processing plants. Only 0.04% is from the nuclear facilities around the Baltic Sea (something that is rarely mentioned by the anti-nuclear groups, it somehow ruins their argument).
>> The activity decreases slowly due to dilution from the rivers that enter the Baltic Sea, but in comparison with other waters in the world this is a rather slow process due to the closed system with only a narrow exit between Sweden and Denmark (see this map that indicates all areas where water systems go into the Baltic Sea: http://www.grida.no/baltic/related/balans_lc.jpg).
>> Less than 2.5 Bq/kg is considered to be a "normal" level, and the goal is to reach that level within a foreseable future.
>> Therefore the levels near Fukushima, in an open sea basin of very large volume (the Pacific Ocean), is of concern. Please note that the article mentions that it is for bottom-dwelling fish. There may be hot-spots in the bottom sediments (there are some in the Baltic Sea with rather high levels, several 100 kBq/m2) that locally will supply fish with high levels for a very long time. So it will have to be investigated closely and monitored for a long time. Ironically, a ban on fishing in the area may have some positive effects on the local marine life, no risk for over-fishing.
>> Anybody interested in more details about the radioactivity levels in the Baltic Sea is recommended to read the Baltic Sea Environment Proceedings No. 117 published by HELCOM (Helsinki Commission - Baltic Marine Environment Protection Commission) in 2009.
>> Best wishes for the weekend,
>> Mattias Lantz
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