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Radiation levels in Japan

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kowalskil

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1) Those interested in recently (?) measured radiation levels (at different distances from the Fukushima reactors in Japan) should see:

 http://www.meti.go.jp/earthquake/nuclear/pdf/monitor02_01.pdf  

(dose levels measured 1 meter above the ground)

 http://www.meti.go.jp/earthquake/nuclear/pdf/monitor02_02.pdf

(dose levels measured 1 centimeter above the ground)

Radiation levels near the Fukishima reactors

Note that the color code is explained near the lower left corner of each dispay. Radiation levels are expressed in micro-Sieverts per hour. [The 10 micro-sieverts, for example, is the same as 0.01 mSv, etc. And 10 micro-Sievert/hour is the same as 0.24 mSv/day, or 7.2 mSv/month.]

2) The effect of penetrating radiation on a person depends on the dose received. The common unit of dose is Sievert (Sv). Smaller doses are expressed in milliseverts (mSv) or microseveret.

A dose of 10 Sv will most likely results in death, within a day or two.

5 Sv would kill about 50% of exposed people.

2 Sv can also be fatal, especially without prompt treatment.

0.25 Sv = 250 mSv is the limit for emergency workers in life-saving operations.

0.10 Sv = 100 mSv dose is clearly linked to later cancer risks.

0.05 Sv = 50 mSv is the yearly limit for radiation workers.

0.004 Sv= 4 mSv typical yearly dose due to natural radiation (cosmic rays, etc).

0.003 Sv= 3 mSV typical dose from mammogram

Ludwik Kowalski (see Wikipedia)

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So, what's the bottom line from this? On the face of it, it seems that there is no place there that is danger to visit, but the reds and pinks could pose risks if one stays there for many years. Is that true? If so, do things change if one removes (say) the top couple inches of soil from lawns? Also, if the radiation level is 19 micro SV 1 cm over a lawn, what would it be inside a building on which that lawn stands?

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