[ RadSafe ] LNT

Sat Oct 1 08:07:06 CDT 2011

You want an estimate. I can do that. The affinity constant of Sr for DNAP has not been measured, but we can estimate that it is higher than the affinity cionstant of uranyl, which has been measured. It is 10^10 m^-1. That means that at a concentration of 10^-10 M (about 9 ng/l) there is 50% saturation of each DNAP by UO2++. For Sr it is probably around this value maybe even higher. I asked the MELODI group to sposor this research but it was left off the list. As we might imagine. I will try and get round to doing this but not just yet as I have bigger fish to fry.
C

-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu on behalf of Brennan, Mike  (DOH)
Sent: Fri 30/09/2011 19:18
To: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] LNT

I noticed that you didn't address my question on an earlier thread, so I
will paraphrase:  What is the Sr90 carrying capacity of a single mouse
sperm?  If you are contending that Sr90 exposure to the father effects
the offspring through Sr90 atoms attached to the sperm (which was my
interpretation of what you contended; I that was not your intent, please
correct me), then a measurement of utmost importance is how much Sr90
(in terms of number of atoms would, I think, be the most useful measure)
is each sperm packing?  An average will do.  I realize this is probably
a fairly tricky measurement, but all of the rest of the experiment is of
no value until you at least prove that SOME Sr90 makes that trip.  At
very least you can take the number of atoms of Sr90 injected into the
mouse (a known) and the rate of mouse sperm production (probably
available in the literature, especially for people who routinely pimp
mice in their experiments) and come up with a maximum that could be
expected (it would help if you did before-and-after boink measurements
on the mice), and see if that number can reasonably lead not only to
damage, but similar damage in several embryos.  

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Busby, Chris
Sent: Friday, September 30, 2011 1:19 AM
To: The International Radiation Protection (Health Physics) Mailing
List; The International Radiation Protection (Health Physics) Mailing
List
Subject: Re: [ RadSafe ] LNT

Raabe: NONSENSE!  All studies are based on actual average radiation
absorbed
dose to living tissues. This is a physical quantity whether the
source is internal or externa

Busby: It is far from nonsense. This is the problem, Otto. I know that
all studies are based on this quantity. But this quantity is not the
same as the ionisation density at the DNA. Any schoolkid could work that
out with a pencil. Thats why you multiply by 20 for alphas. Why do you
think you multiply by 20 for alphas. It used to be callesd relative
biologcal effectiveness RBE.  Are you saying that a decay in the
cytoplasm has the same carcinogenic effect as a decay in the coiled DNA
of an element chemically bound to it? It seems you are. Take tyritium.
The beta range is so small that ALL the decays in the cytoplasm are lost
energy. So the effects must be due to those few atoms that approach rthe
DNA or some other key target. Yet Tritium has a RBE of 1.0. Therefore
the few atoms that are near the DNA must have a RBE of several thousand
to account for the lost energy ionsining the cytoplasm.  ICRP originally
decided as far back as 1972 to add a weighting factor N to internal e
 mitters that bound to DNA. I was told this by one of the ICRP people in
Stockholm last year. They dropped the idea. But ECRR picked it up
(independently, since we didnt know in 2003 that ICRP had done this).  
Best wishes
C

-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu on behalf of Otto G. Raabe
Sent: Thu 29/09/2011 17:09
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] LNT

At 12:40 AM 9/28/2011, Chris Busby wrote:

>The problem is this question: what is the ionisation density at the 
>target? This includes non targeted effects, then the ionisation 
>density in the cell or cell community. It is clear from experiments 
>with radiation but also other chemical stressors that the dose 
>response in complex, and usually biphasic. As you say, there are 
>different mechanisms at high dose rate than low dose rate. But the 
>local ionisation density is usually orders of magnitude higher for 
>internal than external irradiation and for second event emitters or 
>sequences or cascades the cell may alter its repair state before a 
>second or third hit. My own belief is that hormesis is an artifact 
>arising from a misunderstanding of the position of the point 0,0.
>The current arguments (including the radsafe ones) are very simplistic.
>Chris

NONSENSE!  All studies are based on actual average radiation absorbed 
dose to living tissues. This is a physical quantity whether the 
source is internal or external.

**********************************************
Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
University of California
One Shields Avenue
Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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