[ RadSafe ] Biologic Response to Ionizing Radiation

Mon May 9 10:34:34 CDT 2011

Hi All:   

A good summary of the current state of knowledge is presented in the paper

BIOLOGICAL CONSEQUENCES AND HEALTH RISKS OF LOW-LEVEL EXPOSURE TO IONIZING RADIATION: COMMENTARY ON THE WORKSHOP
Ludwig E. Feinendegen,* Antone L. Brooks,? and William F. Morgan?by

Ludwig E. Feinendegen, Antone L. Brooks, and William F. Morgan

in 

Health Phys. 100(3):247-259; 2011

Best regards;

Ludwig Feinendegen

----- Original Message ----- 
From: "Howard" <howard.long at comcast.net>
To: "The International Radiation Protection (Health Physics) MailingList" <radsafe at health.phys.iit.edu>
Cc: "The International Radiation Protection (Health Physics) Mailing List" <radsafe at health.phys.iit.edu>
Sent: Monday, May 09, 2011 4:50 PM
Subject: [ RadSafe ] Biologic Response to Ionizing Radiation

> Chris,
> Indeed, "Higher forms of life are not possible without vigorous and efficient
> DNA repair mechanisms". 
> Feinendigan and Pollycove presented studies showing something like 10 exponent biologic repair response (hormesis) in irradiated mice, something akin to immunization with viral vaccines (think smallpox) or allergy shots. 
> I hope they will comment. 
> Howard Long
> 
> On May 9, 2011, at 3:13 AM, Doug Huffman <doug.huffman at wildblue.net> wrote:
> 
>> Well said!  Thank you.  Tersely too.
>> 
>> On 5/9/2011 02:32, Chris Hofmeyr wrote:
>>> Hi, Bill,
>>> 
>>> Being alive of course incurs a 100% integrated risk irrespective of the meaning
>>> of safety!. However, the LNT crowd treats living organisms as dead matter, i.e.
>>> with no biological response to (radiation) damage. That is most probably a poor
>>> assumption. Higher forms of life are not possible without vigorous and efficient
>>> DNA repair mechanisms. Aging probably results from the fact that the repair
>>> mechanisms are not quite 100% effective to begin with and weaken with time.
>>> Regards,
>>> Chris
>>> chris.hofmeyr at webmail.co.za
>>> 
>>> On Fri, 6 May 2011 13:42:16 -0400 "Bill Prestwich" <prestwic at mcmaster.ca> wrote
>>> 
>>>> Hi John,
>>>> 
>>>> This is a longer thing I sent regarding a local discussion here at Mac
>>>> arising from the 86 billion radsafe posting.
>>>> 
>>>> I don't think the radsafe posting was meant to be a rigorous discourse, and
>>>> neither is this reply. To set the record straight, the Linear No Threshold
>>>> (LNT) theory is really an assumption that the probability of a harmful
>>>> effect resulting from  exposure to ionizing radiation is directly
>>>> proportional to the effective dose. Ionizing radiation is the capitalist
>>>> form of radiation which evicts electrons from their molecules. Dose is
>>>> defined as the ratio of energy deposited by the radiation to the mass of the
>>>> object in which it is deposited. The adjective effective indicates that a
>>>> crude attempt has been made to take into account the variability of
>>>> effectiveness of different radiation types and the variability of radiation
>>>> sensitivity of different organs. It is not possible to make a quantitative
>>>> assessment for the scenario described in the article.
>>>>            The logical conclusion of the LNT, which has not been validated
>>>> empirically, is that any finite dose produces a finite probability for harm.
>>>> This is incorrectly translated into the statement that science has shown
>>>> there is no safe level of radiation. This is an Orwellian tactic which takes
>>>> advantage of two facts. First there is no scientific definition of safe, and
>>>> the proponents are implying it is zero probability of harm. Second the
>>>> concept of safe is generally treated as binary. Something that is not safe,
>>>> ie is unsafe, is dangerous. Hence the implication is that any radiation
>>>> exposure is dangerous. Now, given that we live on a radioactive planet, eat
>>>> radioactive food, breathe radioactive air, have radioactive bodies and are
>>>> bombarded by radiation from outer space, this means we must conclude that
>>>> the act of living is dangerous.
>>>>            This does however open up an interesting legal possibility. It
>>>> seems to me humanity has a right to launch a class action suit against the
>>>> religious organizations as representatives of God who, after all, bears the
>>>> ultimate responsibility for all this.
>>>>            Finally the general consensus is that it is not possible to
>>>> obtain statistically significant empirical data with which to test the LNT
>>>> assumption in the range of dose equivalents below the regulatory limits. The
>>>> situation is similar to attempting to detect a signal buried in noise
>>>> without the ingenious signal to noise enhancement techniques employed by our
>>>> electrical engineering colleagues. However, given that the assumption
>>>> ignores the known complexities of biological responses and fails to predict
>>>> observed radiobiological phenomena it is clear that the assumption does not
>>>> have a substantial scientific basis.
>>> 
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