Comment 61422

By Zot (anonymous) | Posted March 23, 2011 at 15:09:21

Putting the contaminated water issue in perspective:
The contamination is measured in a unit called a Becquerel (symbol: Bq)
Definition: 1 Bq is the amount of radioactive material necessary to produce 1 radioactive decay per second.

Levels: In Japan the "safe" limit in drinking water for infants is 100 Bq per litre. The levels now being seen in Tokyo water are about 250 Bq per litre. So 1 litre of the "hot" water will produce 250 radioactive decays per second. Is that "a lot"?

Biological background: The environment is full of naturally occurring radioactive material. In Human tissue the vast majority of it consists of radioactive Carbon, C14, and radioactive Potassium, K40.
A 70 kg human body contains about 4,400 Bq of K40 and 3,700 Bq of C14, for a total of 8,100 Bq. Dividing this by 70kg we get a natural radioactivity level of human tissue of about 116 Bq/kg.

So, the present levels in Tokyo water are less than twice what is present in "uncontaminated" human tissue.

That said there is of course the possibility that if things deteriorate at the reactors the fallout problem could become much more acute...

(Source for reference values quoted: "Handbook of Radiation Measurement and Protection", Brodsky, A. CRC Press 1978)

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