RE: NCRP 136

["Jacobus, John (OD/ORS)" <jacobusj@ors.od.nih.gov>]

Jerry,

I believe the purpose of the report is to layout and review the current data

and theories about low dose effects.  And there is a lot of data, some of

which is equivocal as stated in the report.  The research needs for

radiation protection purposes, as outlined in NCRP report 117, are

reiterated.  I think that the focus is on DNA affects because that is the

most obvious effect to demonstrate, and is believed to be the underlying

source of radiation effects.  It is also what we know about the most.  I

really do not think the report rejects  hormesis and adaptive response

out-of-hand.  It does state why it rejects the current data the purports to

show them, which is usually based on reexamination of the data or when

viewed in the context of other studies.  An examination of Table 9.4, for

example, shows a wide range of reported results.  As in all scientific

studies, the evidence should unequivocal or continually demonstrated.



I believe the problem is that biological affects, which can be demonstrated

in cells and animals, including such evidence as hormesis and stimulation,

do not really translate to radiation protection guidelines.  While the

biology does gives an insight into what affects radiation causes, they

cannot address the large variability that in the human population.  Since

our radiation protection guidelines are intended to provide protective

guidelines to all workers, you cannot discriminate against those who are

susceptible to harm.



-- John 

John Jacobus, MS

Certified Health Physicist 

3050 Traymore Lane

Bowie, MD  20715-2024



E-mail:  jenday1@email.msn.com (H)      



-----Original Message-----

From: Jerry Cohen [mailto:jjcohen@prodigy.net]

Sent: Tuesday, October 23, 2001 1:31 AM

To: Jacobus, John (OD/ORS); RadSafe

Subject: Re: NCRP 136 





John, Bjorn, et al,

    Thanks for your comments on the questions I asked regarding NCRP-136.

Perhaps My questions were not clear. From the title of the report, I assumed

that the objective was to evaluate the linear non-threshold (LNT) model as

opposed to presenting a tutorial on radiation effects. Many excellent

textbooks  give a good overview of that subject and I did not see where this

report revealed any  particularly new insights. However, my question related

to how the information discussed in the body of the report led to the rather

muddled conclusion to the effect that the LNT  dose-response model is

reasonable.

    Questions relating to the efficacy of LNT that were not addressed in the

report include: (1)How to deal with the problem that if, in fact there

really is a dose threshold, it would be impossible to prove its existence ,

(2) why the focus on DNA aberration effects to the exclusion of all other

possible effects such as stimulation of immune response, and (3) why is all

the evidence supporting hormesis rejected (i.e. not reflected) in the

conclusions?

. . .

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