Re: NCRP 136

["John Johnson" <idias@interchange.ubc.ca>]

Robert and other radsafers



I have only scimmed through this report, but I don't understan your

disappointment. We had to address the LNT issue when we wrote Report 121,

The Principles and Application of Collective Dose in Radiation Protection. A

concern we had is that low doses received at a low dose rate MAY not have

any effect for SOME people, but unless my could PROVE that they were not LNT

for ALL people, we decided that we had to assume LNT.



I think the issue is; Should RP procedures and regulations provide ADAQUATE

protection for everyone, regardless of age, sex and genetic background.- I

think they should!



That doesn't mean that LNT should be used for risk/benifit or similar

calculations.



John R Johnson

Past NCRP member



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

From: Robert A Scott <bobscottchp@JUNO.COM>

To: <radsafe@list.vanderbilt.edu>

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

Subject: NCRP 136





> I too was disappointed with the conclusions of the committee in this

> report.

>

> The Executive Summary states that the committee "was charged to reassess

> the weight of scientific evidence for and against the linear-nonthreshold

> dose-response model, without reference to associated policy implications.

>  The evaluation was prompted by the need to reassess the common use, for

> radiation protection purposes, of the linear-nonthreshold dose-response

> hypothesis......."

>

> To this reader's mind, there was a growing body of new evidence which

> directed one to see a need to reassess the hypothesis.

>

> However, on page six of the report it states "In conclusion, the weight

> of evidence, both experimental and theoretical, suggests that for many of

> the biological lesions which are precursors to cancer (such as mutations

> and chromosome aberrations) the possibility of a linear-nonthreshold

> dose-response relationship at low radiation doses cannot be excluded."

>

> That says to me that this committee ignored the growing body of new

> evidence, and looked at the TOTAL WEIGHT OF EVIDENCE as it stands at the

> moment.  Of course, the TOTAL weight of the evidence is going to be

> fairly evenly distributed for and against the LNT hypothesis.  The fact

> that the LNT cannot be excluded says to me that the bulk of the NEW

> evidence weighs HEAVILY against the LNT hypothesis.  I suspect that the

> committee, despite the fact that it was to reassess the evidence without

> reference to associated policy implications, did in fact take into

> consideration associated policy implications.  Too bad.  We'll have to

> wait another 10 years before the NCRP "reassesses" the matter.

>

> Bob Scott, RSO

> Roger Williams Medical Center

> Providence, Rhode Island

> bobscottchp@juno.com

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