[ RadSafe ] BEIR VII

[Dale Boyce]

Hi all,

I periodically like to point out when discussions like these arise that if 
you take American Cancer Society data on cancer death rates by state and 
plot them versus the mean altitude of the state there is a strong 
anti-correlation.  That is the higher you live (and therefore the higher 
your probable background exposure) the lower your risk of dying of cancer.

This is not an argument for or against hormesis. Just that if low level 
exposure is harmful, it is much less so than the other differences between 
the high and low states, such as heavy industry and air pollution tend to be 
more common at lower altitudes because of accessibility to heavy transport 
methods. It also show that the death rates vary by +/-20 state to state from 
the national mean. How can someone say with a straight face that 100 mSv 
causes an increase of 1% in cancer?

Another thing that I like to throw in every once in awhile is that the 
linear model was developed from high dose data.  (I never get any takers on 
answering this one) At high doses RBE's and Quality Factors do not apply. 
The average dose to an individual cell is the same whether from a 100 rads 
(1 gray) of photons or for example neutrons. Therefore, if we take the 
linear model to low dose it should only work for high LET radiation. Where 
an individual cell receives a similar dose as at high dose. Just a much 
smaller fraction of the cells are exposed. These last two sentences are 
fundamental to the LNT hypothesis.

So for low LET radiation I would argue that the LNT model should fail 
because both the average cellular dose, and the fraction of cells exposed is 
smaller (once you reach a small enough dose). To me this would indicate that 
(IF the LNT model is correct for high LET radiation) then the dose response 
at low dose should go as something like the square of the low LET dose. I 
usually say it in a different way. At low dose of low LET radiation you 
should divide the LNT by the RBE/QF's of high LET radiation.

This also points to another problem with the LNT model. Since we don't use 
the QF's at high dose what unit is the LNT linear in?

In an offline discussion awhile back with another RADSAFER we were 
discussing this last point about not using QF's at high dose. It makes sense 
from a microdosimetry standpoint, and seems to be a fairly commonly held 
view.  However, neither of us could find a reference to support this. 
Anyone know?

Another question. At 40 years post Hiroshima/Nagasaki the excess cancer 
deaths in those populations was something like 250 out of a cohort of 80,000 
or so. Does anyone have the most current figure?

dale

daleboyce at charter.net



----- Original Message ----- 
From: "Michael, Joey L" <joey-michael at uiowa.edu>
To: <radsafe at radlab.nl>
Sent: Thursday, June 30, 2005 3:42 PM
Subject: RE: [ RadSafe ] BEIR VII


>
> Just curious.  What is the official number for background?  It seems to
> me that there has to be a threshold (the threshold is the value of
> background).  Realisticly I know it is a range and depends on your
> location etc.  So within the range of background for various locations,
> it seems that LNT would have to fall apart.
>
> Here is my example.  A group of 10,000 people live in Town X with a
> background of 3.6 mSv/yr.  They live ther for 1/2 yr.  They all move to
> Town Y which has bkg = 7.2 mSv/yr.  They are exposed to an average bkg =
> 5.4 mSv for the  year.  Now, since 5.4 mSv is > 3.6 mSv/yr of Town X
> (1.8 mSv difference), is there an additional risk of cancer (1 in 5556)
> or is the risk = 0 because they were exposed to <bkg for Town Y.
>
> It seems like the risk changes by moving to a different town, and is not
> consistant with the amount of exposure.
>
> Thanks for indulging me,
>
> Joey Michael
> Health Physicist Assistant
> University of Iowa
> Health Protection Office
> 335-8501
>
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