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How to Look at Radiation Levels

By now you’ve probably heard about the recent spike in radiation levels detected in Ibaraki and Kanagawa prefectures. They say it is about 10 to 100 times the “usual level”. Those numbers don’t mean anything to me. The question is: are those measured levels of radiation still with the acceptable range or is it beyond what my body can handle and cause severe damage to my health?


So I want you to check out this neat chart I found to put things in perspective.

Putting the radiation levels at Fukushima into perspective

This is the explanation by gakuranman, the guy who posted the chart:

Here’s a chart showing the range of radiation levels in milli sieverts (mSv). Currently up to 400mSv per hour are being recorded in the immediate vicinity of Fukushima. Remember, although these figures may suggest that the level of radiation being recorded at Fukushima is not extremely high, the danger is constant exposure over a period of time. For this reason, people within the 20km evacuation zone are at high risk of serious harm.

7,000-10,000mSv – Person dies from radiation poisoning. (Full body exposure).
1,000mSv – Nausea and vomiting (Full body exposure).
500mSv – Decrease of lymphocytes in peripheral blood (white blood cells that defend your body) (Full body exposure).
200mSv – No clinical conditions confirmed below this number
10mSv – 1 year’s worth of natural radiation (Brazil)
6.9mSv – CT scan
2.4mSv – 1 year’s worth of natural radiation (world average)
1mSv – Limit of one’s year’s exposure to non-natural radiation (excluding medical examinations)
0.6mSv – Stomach X-ray
0.2mSv – A return air trip from Tokyo to New York
0.05mSv – Chest X-ray (or the level of radiation expected around a nuclear power plant – in practice it is much lower than this)

Source: http://gakuranman.com

The chart shows radiation levels measured in units of milli Sieverts. So let’s do a little math here.

Recent spike measured in Tokyo was around 1 micro Sv (I think the usual is about 0.1 micro Sv). If 1 milli Sv is 1000 micro Sv, then today’s spike was about 0.001 milli Sv.

The media might say: oh it’s 10 times the normal level! If the normal level was 0.0001 milli Sv, then even 100 times the normal level would be 0.01 milli Sv. And that is just 1/5th of a chest X-ray.

Of course, we still have to be careful because the longer you are exposed, more radiation adds up. So take caution.

UPDATE: A similar chart was featured on Daily Yomiuri Online. Check out the full article here.

Radiation exposure, health hazards

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