Re: natural and un-natural radiation

[Jim Muckerheide <jmuckerheide@delphi.com>]

I agree with Bernie. But to go a step further: MOST radiogenic DNA damage is
NOT caused by such direct 'hits.' 

Instead it is caused by DNA interaction with reactive oxygen species that are
formed in the vicinity of the DNA by ionizations. So the DNA is even further
'removed' from 'knowing' that the cause is even ionizing radiation! much less
"natural" vs. "unnatural" radiation!  (There's no such thing, of course -
"radiation" is alpha, beta, gamma, and other "natural" sources, e.g., high
energy particles, protons from cosmic rays, and electron capture and other low
energy transformations). 

But go even further:  The formation of reactive oxygen species by normal
metabolism is millions of times greater than background radiation. (You are
taking your anti-oxidants every day aren't you?  :-)  

Note that the normal "background" level of damaged DNA is about 30,000 in
every cell, with a half-time of repair of 30-40 minutes). This has a high
transient effect with thermal stress, e.g., exercise, drink a hot cup of
coffee, etc.  Certainly the DNA break couldn't give a DAMN whether an OH-
radical was caused by radiation at all!  

Regards, Jim
muckerheide@mediaone.net
Radiation, Science, and Health
==============================

Bernard L Cohen wrote:
> 
> On Sun, 30 Apr 2000, Kjell A. Johansen wrote:
> 
> > Just a couple of comments to this ongoing debate with Norm Cohen.
> > First of all to Steven Dapra, Jay Gould is approximately correct, a
> > change from 24.4 to 24.6 is about an increase of 1%.  Take the
> > difference and divide by the original and you get 0.2/24.4 which is
> > roughly 1%.
> > Next Norm Cohen, radiation is radiation.  For example, UV is UV.  You
> > can get just as much of a sunburn from a tanning salon as from the sun.
> > The body just does not differentiate.  The body reacts to a 5 MeV alpha
> > from a naturally occurring radionuclide the same as it does to a 5 MeV
> > alpha from a reactor product.
> 
>         --Myfavorite way of saying this is that when a DNA molecule in a
> cell nucleus gets hit by an alpha particle (or gamma ray, or energetic
> electron), there is no way for the DNA molecule to "Know" whether that
> alpha particle came from a natural or from a man-made source. The effects
> must therefore be the same.
> 
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