Trivia question, sort of...

[gregsackett@radix.net (Greg Sackett)]

Hello all...

I am currently reviewing the DACs listed in 10 CFR 835 for inconsistancies,
as well as comparing them with other listings. While plowing through hundreds
of DACs, I ran upon a couple that piqued my curiousity:

Nuclide                        D                         Y
--------------          --------------          -------------
Gd-148                    3.E-12                 1.E-11
Gd-152                    4.E-12                 2.E-11

These are for inhaled retention classes (obviously), in uCi/ml.

Can anyone tell me why these are so low? 

I looked at the energies and half-lives:

Gd-148          75 y  with a 3.18 MeV alpha
Gd-152          1.1E14 y with a 2.15 MeV alpha

I can almost understand Gd-152 because of the extremely long half-life,
but with such low energies, why are the limits so low? Other isotopes
of Gd are in the 1E-6 to 1E-8 range, so it shouldn't be a chemical toxicity.
The bone surface is the target organ...

Any ideas?

Thanks!

Greg
*******************************************
Greg Sackett
Health Physicist
Program Management, Inc.
W: (301) 353-1600     fax: (301) 353-1606
gregsackett@radix.net

Texas A&M University, Class of '93, '95
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