Re: LNT Mechanisms

["Jerry Cohen" <jjcohen@PRODIGY.NET>]

If the only determinent of radiation induced cancer was DNA aberation,

this assessment could be a valid affirmation of LNT. However, there

are likely a multiplicity of mechanisms  affecting  cancer induction,

not the least of which are immunicalogical in nature. Radiation exposure

could simultaneously effect all of these mechanisms either positively

or negatively. I doubt that the simplistic assumptions in this study

address the whole spectrum of possibilities.







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

From: <epirad@mchsi.com>

To: <radsafe@list.vanderbilt.edu>

Sent: Friday, May 09, 2003 1:36 PM

Subject: LNT Mechanisms





> Interesting recent paper on the LNT issue.

>

> J Radiol Prot 2003 Mar;23(1):53-77

>

> A contribution to the linear no-threshold discussion.

>

> Chadwick KH, Leenhouts HP, Brugmans MJ.

>

> Department of Biological Sciences, Lancaster University, Lancaster LA1

4YQ, UK.

> kennethhchadwick@aol.com

>

> The paper approaches the linear no-threshold (LNT) hypothesis, currently

used

> as the basis for recommendations in radiological protection, from the

point of

> view of the radiation mechanism. All considerations of the validity of the

LNT

> hypothesis based on experiment or epidemiology are dismissed because of

the

> impossibility of deriving statistically significant data at very low

doses.

> Instead, the LNT hypothesis is assessed from a consideration of the

mechanism

> of radiation action. The DNA double-strand break is proposed to be the

crucial

> radiation-induced molecular lesion. A trace is made using a series of

> correlations that link the DNA double-strand break to effects at the

cellular

> level and these cellular effects are linked to the induction of cancer.

> Multistep modelling of carcinogenesis is used to take the link through to

a

> consideration of radiation risk. It is concluded that, from the point of

view

> of radiation mechanism, at very low doses the LNT hypothesis of radiation

> action is valid, that is, the risk function has a positive slope from zero

dose.







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