[ RadSafe ] Calculated Health Impacts of Reducing NaturalBackground Ionizing Radiation

Muckerheide, James jimm at WPI.EDU
Thu Apr 6 19:44:53 CDT 2006

Bobby,  Also, have you followed DOE's development of a very low background
mine to support research?  My impression was that it is somewhere near you.
Ludwig and Carmel visited the site recently.  I figured they were part of a
research advisory group on the development.

Regards, Jim 

> -----Original Message-----
> From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of
> Scott, Bobby
> Sent: Thursday, April 06, 2006 6:47 PM
> To: radsafe at radlab.nl
> Subject: [ RadSafe ] Calculated Health Impacts of Reducing
> Ionizing Radiation
> Related to writing a chapter entitled "Radiation Hormesis and the
> Control of Genomic Instability" for a Nova Science Publishers, Inc. book
> with the tentative title "New Research on Genomic Instability," I now
> have some new modeling results that led to the following conclusions:
> 1.  Reducing current natural background ionizing radiation to near zero
> would be expected to lead to significant increases in cancer and other
> genomic instability associated diseases as well as increased mortality
> from these diseases.
> 2. A significant reduction in life expectancy would therefore be
> expected to be associated with reducing natural background ionizing
> radiation to near zero.
> I recognize that it may not be possible to reduce natural background
> ionizing radiation to near zero; however, carrying out calculations of
> the expected health consequences can be quite informative, especially in
> light of the widely circulated claims by some (largely in the US) that
> any amount of ionizing radiation is harmful (linear, no-threshold [LNT]
> hypothesis).
> Our modeling research shows that at current natural background radiation
> levels and at lower levels, the risk of radiation-induced cancer should
> be governed by the degree to which a system of protective biological
> processes (normal DNA repair/apoptosis, presumed related to the p53
> protein; an auxiliary apoptosis process that selectively removes
> genomically unstable cells and is presumed to be independent of p53; and
> immune system stimulation) is activated. This system of transient
> protection against harm is activated by low doses of low-LET radiation
> including natural background low-LET radiation.  Dose somewhat above
> natural background radiation also activate the protection.  We call this
> form of low-stress activated protection "adapted protection."  Our
> dose-response models for low-dose radiation-induced stochastic
> biological effects are called "adapted protection models".  Adapted
> protection is a form of hormesis, thus our models are also called
> hormetic models.
> Natural background radiation doses above a stochastic threshold (which
> varies for different individuals) probably over and over activates the
> indicated system of protection, which is transient.  Background low-LET
> radiation (including gamma rays associated with radon progeny) doses
> accumulated over a few weeks may be sufficient for activating the
> transient protection.  High-LET alpha radiation by itself appears not to
> activate the protection, based on limited data for neoplastic
> transformation. Each of us likely has a different threshold for
> activating the indicated protection.  Below the minimum threshold, no
> protection from the indicated system is expected in anyone.  Low
> fidelity DNA repair which is error-prone may operate below the threshold
> but it is also possible that no repair would occur.  Above the maximum
> threshold, each of us are expected to have the system of protection
> activated, but not if the doses are too high where a second stochastic
> threshold comes into play and inhibits a significant amount of
> protection.  This second threshold however appears to be quite large in
> comparison to natural background radiation and probably depends on dose
> rate (increasing as dose rate is reduced). These stochastic thresholds,
> guarantee nonlinear dose-response curves for radiation-induced effects
> such as mutations, neoplastic transformation, and cancer.
> According to the LNT hypothesis, reducing a natural background radiation
> (low- plus high-LET) dose of 0.05 mSv to 0.0000000005 mSv (eight-fold
> lower) would be expected to reduce the risk of cancer by a factor of
> 100,000,000. In contrast our adapted protection modeling results
> indicated that such a dose reduction would be expected to lead to the
> loss of low-dose-radiation (low-LET component) induced adapted
> protection leading any where from a modest to an astronomical increase
> in cancers and other genomic instability associated diseases.  New
> funded research is needed to reduce the indicated uncertainty.
> The adapted protection indicated when activated by low-level, low-LET
> radiation can reduce the cancer incidence to far below the spontaneous
> level.  Many epidemiological and ecological studies have shown this.
> Unfortunately, poorly designed epidemiological studies of nuclear
> workers have apparently misinterpreted adapted protection to be a
> healthy worker effect.  Such studies should be designed to allow
> distinguishing between the healthy worker effect and adapted protection.
> Funding agencies should insist on this for future nuclear-worker-based
> studies that they fund.
> In closing, our modeling results should bring pause to those who have in
> the past not hesitated to make dire predictions of large numbers of
> cancer deaths after low-level radiation exposures of large populations
> based on the LNT hypothesis.  I thought that readers of the Radsafe
> Digest would like to know about our new findings.  The calculations are
> rather complicated and therefore are not presented here but are included
> in the indicated chapter.  I will submit an e-mail to the digest when
> the chapter is published for those who may have interest in reading it.
> Sincerely,
> Bobby R. Scott
> Senior Scientist
> Lovelace Respiratory Research Institute
> 2425 Ridgecrest Drive SE
> Albuquerque, NM 87108 USA
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