Re: Sr-90 and bone marrow

["Otto G. Raabe" <ograabe@ucdavis.edu>]

At 10:15 PM 8/23/00 -0500, Steven Dapra wrote:
>Aug. 23
>
>	A few weeks ago there was a lot of traffic on RADSAFE concerning a claim
>that Sr-90 goes to the bone and irradiates the immune system thereby
>damaging it.  (I do not want to re-start that thread.)  Instead, I have a
>question about where the Sr-90 is deposited, and its effect(s) when it gets
>to the bone.
***************************************************************
August 24, 2000
Davis, CA

Although it originally starts as a surface deposit, through bone remodeling
processes Sr-90 tends to be uniformly distributed in bone matrix over time
as it behaves chemically very much like calcium. In lifetime beagle studies
of ingested Sr-90 conducted here at my lab in Davis, the irradiation of the
marrow was found to result in an absorbed dose about half of that to the
mineral skeleton. Since Sr-90 and it daughter Y-90 beta emitters (E-bar =
1.13 MeV), the range of irradiation includes the marrow and surrounding
tissues. In these lifetime studies there were no immunological responses,
but we did find myeloid leukemias and bone cancer in some dogs irradiated
at lifetime skeletal doses in excess of 20 Sv.

The claim by some anti-nukes that small exposures to Sr-90 causes
immunological damage, etc., is not supported by radiobiological science.
Small beta irradiation doses from Sr-90 are qualitative the same as other
low LET background irradiation. There is no known or expected risk
associated with the levels of Sr-90 we all have in our bodies and teeth
from past weapons testing fallout. Sr-90 is not being released to the
environment by nuclear power plants in any significant quantity, if any.

Otto
	*****************************************************
	Prof. Otto G. Raabe, Ph.D., CHP
	Institute of Toxicology & Environmental Health (ITEH)
	(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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