Tooth Fairy Project

["Otto G. Raabe" <ograabe@UCDAVIS.EDU>]

March 29, 2001

Davis, CA



The Tooth Fairy Project reports can be found at the anti-nuclear web site

http://www.radiation.org



The average Sr-90 concentration in baby teeth that they are reporting is

about 1.5 pCi per gram calcium in deciduous teeth. That compares with an

average of about 9.5 pCi per gram Ca in 1964 following the main nuclear

weapons atmospheric testing years. Their values may be correct, but I

haven't seem analytical confidence ranges. 



They claim there is a problem because the observed values are greater than

their extrapolated expectation that the level should have gone down

exponentially with a steep slope. Their expectation model is without valid

scientific basis, however. 



The reported average value of 1.5 pCi/gram Ca is about what we would expect

from world-wide fallout from the 20th Century atmospheric weapons tests! By

1964 5 MCi (200 PBq) of Sr-90 had deposited in the northern hemisphere.

That deposition continues to this day, but now at very much lower levels,

of course. With a 29 year half life you might expect the average values to

be about 4 pCi per gram Ca now, assuming that plant and grass and cow

uptake rates are unchanged. If anything, their values are lower than

expected. The lower values that they observed can be explained by reduced

uptake of Sr-90 by plants and cows. 

Assuming the 1.5 pCi per gram Ca is the same in the bone, the average

skeletal dose will be about 0.02 mGy per year, which with appropriate

tissue weighting factors would give an annual whole body effective dose of

about 0.002 mSv (0.2 mrem) per year to bone marrow and 0.0002 mSv (0.02

mrem) per year to bone surfaces. These are trivial doses compared to the

about 3.6 mSv (360 mrem) EDE which we all receive every year from normal

background.



Otto

**********************************************

Prof. Otto G. Raabe, Ph.D., CHP

Institute of Toxicology & Environmental Health

(Street Address: Bldg. 3792, Old Davis Road) 

University of California, Davis, CA 95616

E-Mail: ograabe@ucdavis.edu

Phone: (530) 752-7754   FAX: (530) 758-6140

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