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Re: High natural background at Ramsar

At 11:14 AM 4/6/98 -0500, you wrote:
>In any event, I believe Luckey
>attributed the elevated background rate to be due to an uncommonly high
>concentration of uranium/throium in the soils of Ramsari.

All soils are based on sands, with the addition of clays, organic
materials, and water to make what we like to think of as dirt. In general,
the basic sand in most soils is silica sand, made of silicon dioxide. The
soils in that part of India (southeastern, I believe) contain monazite
sands, which are thoriuim dioxide, with the obvious results in terms of
direct radiation exposure and radon. There is an area in Argentina with
similar soils, and correspondingly high dose rates. I haven't seen total
effective dose equivalent values for these areas, only external exposure
data. I was told 1,400 mrem/y for India and 1,100 mrem/y for Argentina as
average values, with no evidence of higher cancer rates than found in other
similar rural agricultural environments. However, I don't have a reference
for those numbers.

Bob Flood
Dosimetry Group Leader
Stanford Linear Accelerator Center
(650) 926-3793