[ RadSafe ] 'How Low Doses Of Radiation Can Cause Heart Disease And Stroke'

[parthasarathy k s]

Scott Bobby, Dan and others,

You have highlighted some of the frailties of the model. With about 100 years of study ionizing radiation continues to be known as a weak carcinogen, mutagen and teratogen with many articulate scientists like you asserting that it is a beneficial agent. I am pleased to see that you are no more in a minority!

Role of ionizing radiation as a "pathogen" in non-cancer  diseases is likely to be minor. The way DNA repair will influence the overall yield is as indicated by you a very important factor. Also, let us not forget that precious little is known about what happens in the lumen-plaque interface in the arteries. The relative importance of the soft lipid content and the calcified part in the plaques is unknown

Regards
K.S. Parthasarathy





________________________________
From: "Scott, Bobby" <BScott at lrri.org>
To: m.w.charles at bham.ac.uk; Mark Ramsay <mark.ramsay at ionactive.co.uk>; srp-uk at yahoogroups.com; Radsafe <radsafe at radlab.nl>; HASNET-RAD at JISCMAIL.AC.UK
Sent: Sat, 24 October, 2009 5:48:16
Subject: RE: [ RadSafe ] 'How Low Doses Of Radiation Can Cause Heart Disease And Stroke'



Monty and others:

The paper is interesting. The authors use a hypothetical model (spatial
reaction-diffusion model) to come to their conclusion about small doses
of radiation causing cardiovascular disease. With their hypothetical
model, small radiation doses cause the mean chemo-attractant (MCP-1)
concentration to increase linearly with cumulative radiation dose. The
assumed main driver for the increase in MCP-1 is radiation induced
killing of monocytes and a consequent reduction in MCP-1 degradation.
The authors state that the major uncertainty in assessing the low-dose
risk of cardiovascular disease is the shape of the dose-response
relationship, which is unclear in the Japanese data (which relate to a
nuclear blast and high radiation doses rather than to a single or
repeated small doses). Their analysis (based on the hypothetical model
used) suggests that linear extrapolation would be appropriate for
low-dose risk estimation, implying cardiovascular disease risk
associated with even a single small dose. Thus, this is another use of
the linear-no-threshold (LNT) hypothesis, except in this case the
implication is that any amount of radiation could cause cardiovascular
disease.

Unfortunately, with their model there is no replacement of lost
monocytes via normal cell division. Normal cells in the body are lost
each day and are usually replaced.  Also, with their model there is no
repair of damage to DNA (thus apparently all damaged monocytes die in
their model). Thus, in developing their hypothetical model, the
researchers disregarded some rather important basic biology/physiology,
namely DNA repair and cell repopulation. These basis protective
mechanisms are important for human survival. Thus, their model is biased
towards calculating harm from small radiation doses that unlikely exists
(in my opinion).

Regarding epidemiological studies that supposedly demonstrate support
for the LNT risk model, many of these studies employ flawed analysis
methods that favor the LNT model over alternative models (e.g., dose
lagging [throwing away some of the dose]). This is discussed in a number
of recent publications. See for example our paper entitled "CT scans may
reduce rather then increase the risk of cancer." The paper is available
at the following link: www.jpands.org/vol13no1/scott.pdf . Other related
papers follow below:

Tubiana M. The 2007 Marie Curie prize: the linear no threshold
relationship and advances in our understanding of carcinogenesis.
International Journal of Low Radiation, Vol. 5, No. 3:173-204,2008.

Cohen B. The linear no-threshold theory of radiation carcinogenesis
should be rejected. Journal of American Physicians and Surgeons Vol. 13,
No. 3:70-76, 2008. 

Jaworowski Z. The paradigm that failed. International Journal of Low
Radiation, Vol.  5, No. 2: 151-155, 2008.
    
Bobby R. Scott
Lovelace Respiratory Research Institute
Albuquerque, NM USA


-----Original Message-----
From: Monty Charles [mailto:m.w.charles at bham.ac.uk] 
Sent: Friday, October 23, 2009 9:57 AM
To: Mark Ramsay; srp-uk at yahoogroups.com; Radsafe;
HASNET-RAD at JISCMAIL.AC.UK
Subject: [ RadSafe ] 'How Low Doses Of Radiation Can Cause Heart Disease
AndStroke'

I don't think one can be complacent about this...


Dr Monty Charles
Reader in Radiation Physics
School of Physics & Astronomy
University of Birmingham
Edgbaston
Birmingham B15 2TT, UK
Tel +44(0)121 414 3483

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