[ RadSafe ] LNT may or may not be scientific- Regulators neednumbers

Mon May 11 06:20:36 CDT 2009

Dear Dr Feinendegen,

Thank you very much for sending me the paper from Radiology. I had a copy already. I have an "unacknowledged" role in inviting the attention of Professor Tubiana to the dilemma faced by regulators in the wake of apparent contradictions in the conclusions of US National Academy of Sciences and the French Academy. I brought it to his notice on July 4, 2005. Thus:

Dear Prof Tubiana,

I have read the interesting executive summary of  the
report titled “ Dose –effect relationships and estimation of the
carcinogenic effects of low doses of ionizing radiation” from the
French Academy of Sciences and the National Academy of Medicine
released on March 30, 2005.The summary  explains why we should use LNT concept with caution in the case of low doses of ionizing radiation.

The  USNational Academy of Sciences has just published the BEIR VII report
which unequivocally argues that “a preponderance of evidence shows that
even low doses of ionizing radiation such as x-rays and gamma ray are
likely to pose some risk of adverse health effects”. The latter thus
supports the validity of the LNT concept.

When
two learned academies come to opposite conclusions on such an important
topic, the non-specialist members of the public and science writers
have a difficult time. Particularly when the claims are presumably
based on the same set of peer-reviewed papers.

I shall appreciate receiving your views on this dilemma. Unfortunately, the report from the FrenchAcademywas not available to many. It went virtually unnoticed by the media I secured a copy from the radsafe news group. 

Yours sincerely

K.S.Parthasarathy Ph.D
Former Secretary, Atomic Energy regulatory Board

I had correspondence with him. He promised to address the concerns in papers to be published later. I read a few of them. Doubts about the practical aspects of radiological protection remains!

With warm regards
Parthasarathy

________________________________
From: Ludwig E. Feinendegen <feinendegen at gmx.net>
To: parthasarathy k s <ksparth at yahoo.co.uk>; Kai Kaletsch <eic at shaw.ca>; al at solidsurfacealliance.org; radsafe at radlab.nl
Sent: Monday, 11 May, 2009 15:38:19
Subject: Re: [ RadSafe ] LNT may or may not be scientific- Regulators neednumbers

Dear All:

The controversy of the LNT hypothesis and the 
discussion on it is very well displayed in the recent review in 
Radiology.  The paper is attached in PDF format

Best regards, 
Ludwig.  

Ludwig E. Feinendegen, M.D.
Wannental 
45
D - 88131 Lindau
Germany

Tel: +49 8382 75673

----- Original Message -----  
From: "parthasarathy k s" <ksparth at yahoo.co.uk>
To: "Kai Kaletsch" <eic at shaw.ca>; <al at solidsurfacealliance.org>; 
<radsafe at radlab.nl>
Sent: Monday, May 11, 2009 2:29 AM
Subject: Re: [ RadSafe ] LNT may or may not be 
scientific- Regulators neednumbers
Kai Kaletesch, 

You have aptly summarized various views on LNT. In 
all probability, there appears to be threshold doses for each and every end 
point.Till there is satisfactory agreement on the lowest value of these 
thresholds, we have difficulties in arriving at practical ways of enforcing 
radiological protection. Regulators need some numbers as dose limits. 
Discussions on whether or not  LNT has irrefutable scientific basis is 
interesting and rewarding. It is clear that we need not lose sleep on the 
possibility of induction of cancer and other effects at low level 
radiation.State of the art technologies may help us to detect a single 
interaction in cells or tissues; however we need not worry, as, such 
"picoscopic" changes which occur with unpredictable rates, seldom lead to 
macroscopic cellular changes that lead to effects such as 
cancer.

Parthasarathy

________________________________
From: 
Kai Kaletsch <eic at shaw.ca>
To: al at solidsurfacealliance.org; radsafe at radlab.nl
Sent: Sunday, 10 
May, 2009 21:48:38
Subject: [ RadSafe ] LNT

Hi Al,

you 
wrote:

"If LNT is the generally accepted theory..." I think we have to 
look at what "generally accepted" means. If I understand the LNT debate 
correctly, the differing thoughts can be summarized like this:

1) Some 
people believe that LNT is a pretty good model and is no worse than other models 
(hormesis/threshold). So, we might as well keep it.
2) Some people believe 
that  LNT has significant shortcomings and is probably not the correct 
scientific model, but it is easy and convenient to use for making policy. So, we 
might as well keep it, as the basis for making policy.
3) Some people believe 
that LNT is either incorrect or irrelevant at very low doses and the use of LNT 
at very low doses should be restricted. See for example the HPS position 
statement http://hps.org/documents/risk_ps010-1.pdf, which explicitly states : " the Health Physics Society 
recommends against quantitative estimation of health risks below an individual 
dose of 5 rem in one year or a lifetime dose of 10 rem above that received from 
natural sources."
4) Some people believe that there is strong evidence that 
LNT fails. Some of these people think that it is time to adjust public policy 
accordingly. Others think that this should be a scientific debate and public 
policy should not be an issue.

While some of the politically appointed 
bodies still cling to 1), it seems to be the minority position among scientists. 
The HPS states: "There is, however, substantial scientific evidence that this 
model is an oversimplification. It can be rejected for a number of specific 
cancers, such as bone cancer and chronic lymphocytic leukemia, and heritable 
genetic damage has not been observed in human studies. However, the effect of 
biological mechanisms such as DNA repair, bystander effect, and adaptive 
response on the induction of cancers and genetic mutations are not well 
understood and are not accounted for by the linear, no-threshold 
model."

There used to be people who thought that LNT was actually a 
correct description of the organism's response to radiation. This was before we 
knew about biological mechanisms such as DNA repair, bystander effect, and 
adaptive response. I have not heard any credible scientist state, in the last 10 
years, that he/she personally believes that LNT is the scientifically correct 
model and that it describes the dose response 100% correctly for all types of 
ionizing radiation.

It would be extremely easy to prove me wrong on this. 
All it would take is for someone on this list to state that they personally 
believe that LNT is the scientifically correct model that it describes the dose 
response 100% correctly for all types of ionizing radiation.

It will be 
interesting to see if there is still anyone out there who truly accepts LNT as a 
scientific theory.

Best Regards,
Kai

----- Original Message 
----- From: <al at solidsurfacealliance.org>
To: <radsafe at radlab.nl>
Sent: Thursday, May 07, 2009 4:45 PM
Subject: [ RadSafe ] Re: 
radsafe Digest, Vol 196, Issue 3

"I listen with interest when people 
talk about hormesis
and/or thresholds, and await models and studies that 
would elevate one
of those concepts to the dominant paradigm 
status."

Excellent point and one that if logic rules the discussion, 
ends the discussion. If LNT is the generally accepted theory, any claims to the 
contrary have the burden of proof. If the BEIR committee changes their position 
on LNT, I will be convinced. Prior to that, right or wrong, the radiation is 
chocolate crowd will lack credibility.

Al

be or unsubscribe 
and other settings visit: http://radlab.nl/radsafe/

_______________________________________________
You are currently 
subscribed to the RadSafe mailing list

Before posting a message to 
RadSafe be sure to have read and understood the RadSafe rules. These can be 
found at: http://radlab.nl/radsafe/radsaferules.html

For information on how to subscribe or unsubscribe and other 
settings visit: http://radlab.nl/radsafe/