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Re: Science and LNT
LNT is NOT "the best we can do today- unless that possibility [it disproven]
were a virtual certainty".
Do you have "virtual certainty" of safety when you drive your car?
What is the harm from NOT driving your car, or of NOT having the now likely
benefit of 10 X the usual background radiation (less cancer and better
longevity)?
Is it prudent to not operate on appendicitis because of the risk of surgery?
Sometimes.
Competent risk analysis requires the 2-tail test, weighing BENEFIT against
harm and considering individual variation.
Howard Long
----- Original Message -----
From: <niton@mchsi.com>
To: <radsafe@list.vanderbilt.edu>
Sent: Thursday, September 25, 2003 6:27 AM
Subject: Science and LNT
>
>
> J Radiol Prot. 2002 Sep;22(3A):A129-35.
>
> Uncertainty, low-dose extrapolation and the threshold hypothesis.
>
> Land CE.
>
> Radiation Epidemiology Branch, Division of Cancer Epidemiology and
Genetics,
> National Cancer Institute, Bethesda, MD, USA.
>
> Risk-based radiation protection policy is influenced by estimated risk and
by
> the uncertainty of that estimate. Thus, if the upper limit, at (say) 95%
> probability, of risk associated with a given radiation dose is at
> an 'acceptable' level, it is unlikely (or not credible) that the true
level of
> risk associated with the dose is at an unacceptable level. Central
estimates
> presented alone, in the absence of probability limits, lack this safety
> factor. Estimating cancer risks from low doses of ionising radiation
involves
> extrapolation of risk estimates based on high-dose data to the much lower
dose
> levels that characterize the vast majority of exposures of regulatory
concern.
> Proof of a universal low-dose threshold, below which there is no
radiation-
> related risk, would revolutionise radiation protection. Available data
fail to
> provide such proof and, in fact, leave considerable room for the
possibility
> that DNA damage from a single photon can contribute to the carcinogenic
> process. Allowing for the possibility of a threshold would, however,
remove
> very little of the regulatory burden associated with the so-called linear,
no-
> threshold hypothesis, unless that possibility were a virtual certainty.
>
>
> INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF RADIOLOGICAL PROTECTION
> J. Radiol. Prot. 23 (2003) 263-268 PII: S0952-4746(03)65206-7
>
> The LNT model is the best we can do-today
>
> R Julian Preston
> Environmental Carcinogenesis Division, National Health and Environmental
> Effects Research Laboratory, US Environmental Protection Agency (MD
B143-06),
> Research Triangle Park, NC 27711, USA
>
> E-mail: preston.julian@epa.gov
>
> Received 10 February 2003, in final form and accepted for publication
> 27 May 2003
> Published 8 September 2003
> Online at stacks.iop.org/JRP/23/263
>
> Abstract
> The form of the dose-response curve for radiation-induced cancers,
particularly
> at low doses, is the subject of an ongoing and spirited debate. The
present
> review describes the current database and basis for establishing a low
dose,
> linear no threshold (LNT) model. The requirement for a dose-response model
> to be used for risk assessment purposes is that it fits the great majority
of
> data derived from epidemiological and experimental tumour studies. Such is
the
> case for the LNT model as opposed to other nonlinear models. This view is
> supported by data developed for radiation-induced mutations and chromosome
> aberrations. Potential modifiers of low dose cellular responses to
radiation
> (such as adaptive response, bystander effects and genomic instability)
have not
> been shown to be associated with tumour development. Such modifiers tend
> to influence the slope of the dose-response curve for cellular responses
at low
> doses and not the shape-thereby resulting in a quantitative modification
rather
> than a qualitative one. Additional data pertinent to addressing the shape
of
> the tumour dose-response relationship at low doses are needed.
> > From: Ted Rockwell [mailto:tedrock@starpower.net]
> >
> > >I don't know of any good data that show deleterious effects from LDR.
> >
> > But there is some evidence, and some logical arguments, that create a
> > reasonable doubt about dose and effect at low levels, IMHO.
> >
> > >And they rely only on the demonstrably false argument that it is
> > prudent to assume the worst. That is not science. It is transparently
> > politics.
> >
> > I guess "they" here are the NCRP and ICRP. What they are doing is
> > transparently setting policy. These policies are based on science, but
> > no, they are not "science". I think it is good policy to be prudent
> > until we have the clear evidence or a unified and well confirmed model
> > that eliminates this reasonable doubt. I agree that funding should be
> > fairly distributed to different groups, although I've never seen real
> > fairness in funding in any area of science. The burden is and should be
> > on those who believe in a threshold to show convincingly that it exists
>
> > and what its numerical value is, before public policy should be shifted
> > away from prudence. I found Mossman's "the debate is over" unpalatable,
> > as I do the arguments of those who say "low levels are clearly
> > harmless". This scientific discussion is clearly not resolved, and my
> > point (in the context of this thread) was that we should be honest about
> > that among ourselves and when dealing with the public and others.
> >
> > Mike
> >
> >
> > Michael G. Stabin, PhD, CHP
> > Assistant Professor of Radiology and Radiological Sciences
> > Department of Radiology and Radiological Sciences
> > Vanderbilt University
> > 1161 21st Avenue South
> > Nashville, TN 37232-2675
> > Phone (615) 343-0068
> > Fax (615) 322-3764
> > Pager (615) 835-5153
> > e-mail michael.g.stabin@vanderbilt.edu
> > internet www.doseinfo-radar.com
> >
> >
> >
> >
>
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