[ RadSafe ] The Role of Low-Dose Radiation in the Maintenance of Life

Fri Nov 3 14:50:17 CST 2006

Dr. Scott,
Thank you for the reply.  Yes, I understood that you
are not involved with human research.  Nevertheless, I
think the work you are doing is important if not for
the same reasons you do.  I resently attended a
lecture by Dr. William S. Dynan of the Medical College
of Georgia on the repair of ionizing radiation-induced
DNA double-strand breaks and implication for
therapeutic treatment.  The work was funded in part by
the DOE low-dose program.  

Nevertheless, nothing that you write about Low dose
effects and the fear of radiaiton is really not that
new.  I and others have heard the arguements before. 
I am not impressed by the claims.  I am certainly
willing to change my mind, but so far the human data
does not appear to me to be that significant.  

I have been in radiation safety and health physics
since 1975.  I have and currently answer questions
people have about medical exposures to themselves and
their children.  Not once have I heard them mention
the LNT.  They do have concerns about radation
exposure, and I try to respond to their concerns
directly.  We know that there are no observable
effects below 10 rem.  All the research on cells,
tissues and mice is not their concern.  The adaptive
response is certainly evident, but they did not get a
stimulating dose before their medical x-ray.  Do you
get a stimulating dose before a medical or dental
x-ray?  

--- "Scott, Bobby" <BScott at lrri.org> wrote:

> 
> John:
> 
> Thanks for your interest in our low-dose radiation
> research. For
> clarification, we are not monitoring irradiated
> humans.  Our research
> mainly focuses on researching, interpreting, and
> reporting research data
> (molecular, cellular, tissue/organ, and systemic
> levels) obtained by
> other scientists.  That low doses of low-LET
> radiation can protect
> (sometimes called adaptive response and sometimes
> called hormesis)
> against stochastic effects such as mutations,
> neoplastic transformation,
> and cancer is now becoming widely published.  Doses
> as low as 0.02 mGy
> of ionizing photon radiation induce protection
> (suppressed spontaneous
> mutations) in animal studies.  Low-dose data from
> numerous
> epidemiological and ecological studies of
> radiation-induced cancer show
> evidence for radiation suppressing cancer rather
> than increasing cancer.
> The data involve a wide range of doses and dose
> rates. A paper (Chuck
> Sanders is first author) has been submitted for
> publication which
> discusses much of the indicated data showing cancer
> suppression by low
> doses and dose rates or low-LET radiation or
> combinations of low and
> high-LET radiation.  The paper relates to a
> presentation given at the
> 2006 International Hormesis Society Conference.
> 
> Increase cancer risk after low doses of low-LET
> radiation (or
> combinations of low and high-LET radiation) is
> essentially created by
> using an in appropriate risk modeling assumption for
> characterizing the
> risk at low doses.  The most popular but incorrect
> assumption used is
> that any amount of ionizing radiation, including
> low-LET radiation, is
> harmful, and that cancer increases linearly with
> dose. This model
> assigns increased risk even for natural internal
> irradiation of our
> bodies (e.g., associate with potassium-40). 
> High-dose-rate and
> high-dose data usually determines the slope of the
> caner risk
> dose-response curve (e.g., data from Hiroshima and
> Nagasaki). Risk at
> low doses and dose rates are then projected based on
> reducing the slope
> of the high-dose-rate dose-response curve by a fixed
> amount (low-dose
> and dose-rate effectiveness factor, DDREF).
> 
> Please note that the claim by experts that any
> amount of radiation is
> harmful led to more than 100,000 lives being lost
> via abortions
> (radiation-phobia driven) following the Chernobyl
> accident, while fewer
> than 10 cancer deaths (thyroid cancer) have been so
> far attributed to
> low-dose radiation exposure in associated with the
> Chernobyl accident.
> Tens to hundreds of thousands of cancer deaths were
> predicted by some
> experts shortly after the accident. 
> 
> Radiation-phobia driven casualties (LNT-related) are
> the current main
> risks in association with low doses of ionizing
> radiation in the event
> of a radiological terrorism incident involving a
> large population and
> low-level, low-LET radiation exposure.
> 
> Regarding the question as to whether low-dose
> radiation provides a weak
> or strong cancer-suppression benefit, in some cases
> it has been a weak
> and in other cases a strong benefit.  Weak benefits
> seem to be
> associated with low doses of low-LET radiation
> delivered at a high rate.
> Strong benefits seem to be associated with low and
> moderate doses of
> low-LET radiation delivered at a low rate over
> years.  Such data are
> discussed in the cited submitted paper with Chuck
> Sanders as first
> author.
> 
> Our research results indicate that the cancer
> suppressive effects of low
> doses of low-LET radiation depend on age, increasing
> with age. Thus, the
> very young may benefit much less from protection
> than the elderly.
> Further, we have not found evidence for a purely
> alpha-radiation source
> inducing protection against stochastic effects.  In
> addition, our
> research has led us to conclude that each person
> likely has a different
> (stochastic) low-LET radiation threshold for
> activating the protective
> processes that suppress cancer occurrence.  Thus,
> for a given low dose
> of low-LET radiation, a person selected at random
> may have a higher
> threshold and in such cases would therefore not be
> expected to benefit
> from the protection.  Thus, we do not claim that a
> specified low dose of
> radiation is necessarily beneficial to all (although
> it may be
> beneficial to most, depending on dose and dose-rate
> histories).  In
> addition, each person is thought to have a higher
> deleterious stochastic
> threshold that inhibits at least some or the
> protection (e.g.,
> suppression of immunity).  The indicated protective
> and deleterious
> stochastic thresholds lead to nonlinear
> dose-response relationships. 
> 
> For readers of the Radsafe Digest who have interest
> in stochastic
> thresholds and their expected impact on
> dose-response curve shape, you
> may find the following publication to be a useful
> reference:
> 
> Scott BR. Stochastic thresholds: A novel explanation
> of nonlinear
> dose-response relationships for stochastic
> radiobiological effects.
> Dose-Response 3:547-567, 2005.
> 
> An upcoming book chapter may also be of interest to
> some Radsafe Digest
> readers:
> 
> Scott BR. Natural Background Radiation-Induced
> Apoptosis and the
> Maintenance of Mammalian Life on Earth. Chapter 1
> in: New Cell Apoptosis
> Research, L.C. Vinter (Editor), Nova Science
> Publishers, Inc.
>
https://www.novapublishers.com/catalog/product_info.php?products_id=4948
> &osCsid=432f071849b59bb26326e99721f8335a
> 
> 
> Sincerely,
> Bobby R. Scott
>  
> 
> -----Original Message-----
> From: John Jacobus [mailto:crispy_bird at yahoo.com] 
> Sent: Friday, October 27, 2006 2:51 PM
> To: Scott, Bobby; radsafe at radlab.nl
> Subject: RE: [ RadSafe ] The Role of Low-Dose
> Radiation in the
> Maintenance of Life 
> 
> Dr. Scott,
> Yes, I have heard the old saw too many times.  I
> prefer caveat emptor.
> 
> Of course dose rate is important.  That is the basis
> for fractionation of radiation therapy.  So does the
> end point of the study.  Exactly what doses and dose
> rates above background are you talking about?  Are
> the
> effects seen in humans?  And what effects are you
> monitoring.  If you monitor the blood of a patient
> and
> find an increase of some cellular component, this
> may
> indicate that the response is due to cellular damage
> and of or the cytokines being released from the
> affected cells.  If the immune cells attack the
> damaged cells and not the undamaged tumor cells,
> what
> is the consequence?  Does the tumor survive?  
> 
> If radiation is recognized as a weak carcinogen, is
> it
> also a weak benefactor?
> 
=== message truncated ===

+++++++++++++++++++
"Give me your tired, your poor, 
Your huddled masses yearning to breathe free, 
The wretched refuse of your teeming shore, 
Send these, the homeless, tempest-tost to me, 
I lift my lamp beside the golden door!" 

>From "The New Collossus" by Emma Lazarus

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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