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Originally Posted by Nyororin
There is no way to avoid all radiation exposure - the human body actually produces radiation... But I get your point.
I think that you have misunderstood the 1/100 figure though. 1 in a hundred is the number of people who have an actual increased risk of cancer - not the number who actually develop cancer... And certainly not the number who become terminally ill.
To be more exact, a single exposure of 100mSv has been shown to raise cancer risk around 0.5~1%. Long term exposure to lower amounts is a completely different matter and is almost impossible to measure. 100mSv over a YEAR is pretty much nothing. There is a fairly large city in Brazil (Guarapari) where the natural background radiation is almost 200mSv a year, and there has been no noticeable difference in cancer rates compared to everyone else. And people live their entire lives there with no decreases in radiation over the entire time.
So, basically, 100mSv a year for those living in Fukushima has such a tiny level of risk that it is impossible to calculate.
It is when you have a single large dose that things start to change and you begin to have an increased risk of developing cancer. A person`s lifetime risk of developing cancer is influenced by a number of things - for example, smoking raises your lifetime risk of developing cancer by anywhere between 2 and 15% (depends on how long and how much you smoke, etc). Drinking raises your risk of developing cancer by so many percent. Regular tanning by so many percent. So on and so on.
This *doesn`t* mean that you will die from cancer - it doesn`t even mean that you will develop cancer at all. It just means that on average, that many more people develop cancer than a group that didn`t do those things.
So... In the case of 1000 people receiving a dose of 100mSv - one extra person might develop some type of cancer as a result. Chances are, it will be thyroid cancer - one of the easiest to treat cancers with an excellent prognosis. In the case of 100,000, you may have one extra case of a more dangerous type of cancer... Out of 2,000,000, think more like 20 extra people with a terminal illness - not 20,000.
Either way though, it`s a moot point in the case of Fukushima as it is 100mSv in a single dose, not spread over a year.
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I have never heard about these cities before. Very Informative!
I found out that Ramsar, Iran has the highest known year-average human exposure levels measured in an inhabited location.
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According to UNSCEAR 2000 report, Ramsar, in northern Iran, has some inhabited areas with the highest known natural radiation levels in the world.
In Guarapari, Brazil, a city of 80 000 inhabitants built on the seaside, peak measurements made by EFN on the thorium-rich beach were as high as 40 microSv/hour (about 200 times higher than the average natural background radiation in other areas of the world).
But the highest known year-average human exposure levels measured in an inhabited location up to date is in Ramsar, Iran.
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Natural Radiation: High Background Radiation Areas (HBRAs) of Ramsar, Iran