[ RadSafe ] Hypothetical post-LNT Rad Limits and Regs
parthasarathy k s
ksparth at yahoo.co.uk
Sun Sep 27 00:00:34 CDT 2015
Hunting for a threshold dose was never successful so far.You may recall that The French Academy which raised formal objection to the scientific validity of LNT conceded that it could not get evidence for any threshold. Additionally, if there is a threshold dose it is likely to be different for different individuals.There is still unsettled debate on the lowest dose which causes cancer. Most critics accept a value of 100 mSv single short term dose. Now the question is what should be the safety factor taken.There may also be some agreement that the safety factor can be more for members of the public which includes sensitive and vulnerable sections such as pregnant women, infants and children. we have accepted a safety factor of 5 for occupational workers; ICRP accepted 100 mSv in consecutive 5 years with occasionally 50 mSv/year.Whether we have to accept one mSv or 5 mSv for public is an equally important debate depending on how conservative we have to go.In all this arguments we seldom indicate to members of the public that there is judgement exercised by scholarly bodies such as the ICRP and NCRP.
Most important factor in these arguments is how to carry all stakeholders in the process of decision making. A few years ago, ICRP realized it.The fact that the members of the public need not necessarily accept the decisions of a dozen specialists however highly regarded was probably an eye opener. The publication of ICRP recommendations on its website, gathering views of all stake-holders, discussing them threadbare were all part of the democratization process.
The perception that everyone on either side of the aisle has an agenda is influencing impartial observers. Rather than naively assuming that public will not understand complex arguments, specialists must develop the tools for effective communication WE must not deny the public a chance to participate in decision making; may be specialists have not yet developed such tools.
Let us grudgingly accept that the true nature of interaction of low doses of radiation with living tissue is not exactly known. So long as interactions at low dose levels are statistical in nature, it will be very difficult to accept error free repairs of the micro damages of tissue at molecular level.A totally maverick approach to the issues is not likely to be acceptable.At the present level of knowledge, it will be foolhardy to believe that deterministic answers must be obtained for purely probabilistic questions.The way forward is to accept and publicize the fact that the risks, if any, at low levels of radiation are too low to be worried about.
On Sunday, 27 September 2015, 2:45, Mark Sonter <sontermj at tpg.com.au> wrote:
Otto is right.
Just apply the limit (with safety margin).
This is what is done with the thousands of (chronic) chemical hazards in
workplaces, about the vast majority of which we have less knowledge of
dose response relationship than we have for radiation.
Except that we know that in general the dose response relationship is
NOT linear but generally sigmoidal...
For all these chemical chronic hazards, and for noise (where we *know*
the relationship is sigmoidal) and for respirable free silica (where we
*know* the relationship is sigmoidal)) we aren't fussed that we don't
have a linear relationship: we simply 'use the limit'.
FWIW, I don't think that walking away from LNT would call for any
*workplace* limit change, but I do think it would allow or facilitate
what we really need which is a return to a formally stated 'de minimus'
annual dose, which should probably be about 1 or 2 mSv, based on the
observation that that is what Mother Nature gives us, and anything lower
is 'down in the noise'.
The real 'problem' has never been the idea of ALARA (which I think is
sensible) or the reduction from 50 mSv to 20 mSv (which is OK altho
probably a bit on the cautious side), but the reduction of Member of
Public dose limit from 5 mSv to 1 mSv. THAT is and has been and always
will be The Problem...
Mark J Sonter
Director & Principal Consultant, Radiation Advice & Solutions Pty Ltd,
abn 31 891 761 435
Co-Founder & Director: Mining & Processing, Deep Space Industries Inc.
116 Pennine Drive, South Maclean, Queensland 4280, Australia
Phone/fax: 07 3297 7653; Mobile: 0447 755598
(delete '0' & replace with '61' country code if calling from overseas)
“Keep everything as simple as possible, but no simpler” - A. Einstein
On 27/09/2015 3:00 AM, radsafe-request at health.phys.iit.edu wrote:
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> Today's Topics:
> 1. Radiation Safety Without LNT (Otto G. Raabe)
> Message: 1
> Date: Fri, 25 Sep 2015 14:56:09 -0700
> From: "Otto G. Raabe" <ograabe at ucdavis.edu>
> To: "The International Radiation Protection \(Health Physics\) Mailing
> List" <radsafe at agni.phys.iit.edu>
> Subject: [ RadSafe ] Radiation Safety Without LNT
> Message-ID: <201509252156.t8PLuIBN006327 at msa3.ucdavis.edu>
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>> September 25, 2015
> When I started radiation safety works in 1958, radiation standards
> were based on limiting exposures based on the International
> Commission on Radiological Protection (ICRP) Publication 2.
> The methods were straight-forward and sound based on
> limiting exposures.
> For example, ICRP 2 page 82 states sound limits for
> internal exposure to plutonium isotopes. For example.
> no plutonium worker was allowed to exceed a
> lung burden of 16 nCi of Pu-239.
> In the early days thousands of workers were exposed including me
> to inhaled plutonium at Los Alamos, Rocky Flats, Handford, Kerr-Magee,
> the Nevada Test Site and elsewhere, but there has been no known
> lung cancer case that were associated with inhaled plutonium-239
> at those facilities..
> ICRP 2 is a good example of how to end the
> Linear-No-Threshold (LNT) fallacy.
> Prof. Otto G. Raabe, Ph.D. CHP
> Center for Health and the Environment
> University of California
> One Shields Avenue
> Davis, CA 95616
> Office: 530-752-7754
> FAX : 530-758-6140
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