The highest background radiation levels I could find are in China, India, Brazil, and Iran (more on this in chapter 17). All these countries have deposits of monazite - a black sand often found on beaches and in rare earth deposits - in which the principle radioisotopes are from the decay of thorium 232 and radium 226.
The 80,000 people of Kerala, India, receive up to 1,300 mrem (1.3 cSv or about three-and-a-half times our background exposure) per year and have been recognized for their healthfulness compared with neighboring states. The 10,000 citizens of Guarapari, Brazil, and the vacationers that flock to their beaches to bury themselves in the black sand absorb 0.03 mGy (3mrem) per hour - the equivalent of 26,280 mrem (2.6 cSv or about eighty-seven times our background) per year. [It is illegal to take the sand, but it has been done for centuries by tourists who have heard of its benefits and keep it under their beds. By so doing they receive little additional "through skin" radiation, but are exposed to continuing sources of breathable radon.]
Meanwhile in Ramsari, Iran, the 2,000 inhabitants and their ancestors have lived for centuries begin exposed up to 48,000 mrem (48 cSv or 132 times the U.S. average) and "survived" to tell about it... in fact they keep on surviving to the point that our regulators are wearing out their fingernails from scratching their LNT - and collective dose - heads. (Actually, they just engage in politically correct science: ignore those data that are inconvenient.)
Table 10 – Background Radiation in Various Locations
with Comparisons
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Case/Place
|
cGy/yr
|
mrem/year
|
Ratio
to U.S. average
|
EPA level of concern
|
0.001
|
1
|
0.003
|
Limit nearby nuclear power plant
|
0.005
|
5
|
0.016
|
Proposed EPA maximum (all sources)
|
0.100
|
100
|
.3
|
U.S. average background
|
0.300
|
300
|
1.0
|
Chernobyl forced resettlement**
|
0.500
|
500
|
1.7
|
Colorado plateau
|
0.600
|
600
|
2.0
|
Kerala, India
|
1.3
|
1,300
|
4.3
|
Gerais, Brazil
|
2.3
|
2,300
|
7.7
|
Hormesis optimum (Luckey)
|
10.0
|
10,000
|
33.3
|
Guarapari Beach, Brazil
|
26.3
|
26,300
|
87.6
|
Ramasari, Iran (average)
|
48.0
|
48,000
|
132
|
* Adapted from “Radiation Hormesis for
Health” by T.D. Luckey, Health Physics
Newsletter, June 1995.
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** In areas where the natural
background plus the Chernobyl contribution exceeded this limit, 200,000
people were forcibly resettled.
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