[ RadSafe ] BEIR VII

[Dale Boyce]

Hi all,

I think people are taking the observation I made too seriously. It was not 
presented as science, just an observation.

Certainly a well controlled scientific study must have a lot more variables 
to consider. The point I was trying to make is that the general trend is for 
higher backgrounds at higher altitudes, both from terrestial and cosmic ray 
sources. However, the general trend is to have higher cancer rates at lower 
altitudes.

I am not claiming that this is any measure of dose response or lack thereof. 
Just that other environmental and/or demographic variables appear to 
outweigh any negative effect that may exist at low dose.

The numbers I remember are that statistically significant excess cancers 
have only been observed in humans at doses of 100 rads (1 Gy) and above with 
the exception of breast cancer in women (0.5 Gy).  I do not remember off the 
top of my head numbers for cancer in children. If there are newer and lower 
statistically significant data, I would like to have a reference.

These numbers are for acute exposures where the dose is approaching or 
exceeding the threshold for acute radiation sickness. It could reasonably be 
expected that repair mechnisms may not work as well if for example the 
individuals immune system is impaired.

The range of the statistically significant data is from about 0.5 to 5 Gy 
acute exposure, and isn't even linear over this entire range since death 
from acute sickness reduces the number of cancers developed at the high end 
of the scale. Extrapolating this to 0.1 Gy acute exposure for regulatory 
purposes is probably not out of line.

However, I still argue that extrapolating it to cover low dose rate 
accumulated over a long period, and using it to estimate the number of 
excess cancers in a population is not appropriate.

I also agree with Jim that using it to justify setting regulatory limits 
that are unreasonably low is wrong. Setting limits of annual exposure to 
individual members of the public lower than about 100 mrem/yr is essentially 
impossible to implement in terms of being able to document.

As an example I once occupied an office that contributed and additional 40 
mrem/year to my exposure compared to that in a nearby building. All due to 
natural radioactivity in the building materials (about 30 uR/hr vs. about 10 
uR/hr).

Another building had this same variation all in the same building. Basement 
through third floor were constructed, and floors 4 through 7 added later. 
The glaze in the tiles on the walls had about 3 times the natural 
radioactivity in the lower floors.

I have seen tiles on one wall produce up to 100 uR near the wall. Note that 
one has to be careful about instrumentation. Thin window instruments may 
pick up the hard beta in the uranium chain, and produce high readings 
compared to measurements made with the beta slide closed.

It is therefore a silly excercise to try to regulate really tiny exposures 
when the variation among individual background exposures varies so much 
depending on where they spend their time in one locality, much less across 
different parts of the country.

Dale



----- Original Message ----- 
From: "Kolb, William (WKOLB)" <WKOLB at arinc.com>
To: "John Jacobus" <crispy_bird at yahoo.com>; <radsafe at radlab.nl>
Sent: Friday, July 01, 2005 7:39 AM
Subject: RE: [ RadSafe ] BEIR VII


> Wouldn't you have to plot the cancer rates against the weighted mean
> altitude of the population?
>
> Bill
> WM Kolb
>
> --- "Otto G. Raabe" <ograabe at ucdavis.edu> wrote:
>
>> At 02:41 PM 6/30/2005, Dale Boyce wrote:
>> >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.
>> ***********************************************
>> Hawaii doesn't fit very well since it is low in
>> altitude and low in cancer.
>>
>> Otto
>>
>>
>
> +++++++++++++++++++
> "Every now and then a man's mind is stretched by a new idea and never
> shrinks back to its original proportion." -- Oliver Wendell Holmes, Jr.
>
> -- John
> John Jacobus, MS
> Certified Health Physicist
> e-mail:  crispy_bird at yahoo.com
>
>
>
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