Re: linear hypothesis

[mgoldman@ucdavis.edu (Dr. Marvin Goldman)]

>I guess it's time to chime in on this subject. The American Nuclear
>Society and the Health Physics Society both are looking at the validity
>of the linear hypothesis (LH). The ANS has had two meetings at which a
>number of papers were presented that cast doubt on the LH. In a recent
>issue of Nuclear News, Jim Muckerheide summarized information that adds
>to that doubt. The Winter meeting of the ANS will contain two days of
>papers and panels on the LH. That meeting is in San Francisco on October
>30 - November 2, 1995 at the Hilton Hotel and Towers. The LH papers and
>panels are on October 31, November 1, 1995.
>
>The HPS Newsletter of June, 1995 is a special issue on the LH. There
>were 22 letters, all opposing the LH, in that issue. The HPS is
>preparing a position paper on the LH. Hopefully, that paper will be
>available shortly.
>
>I received a reply to a letter I wrote to Charlie Meinhold, chair of
>NCRP, ICRP and IRPA in which I asked him: "...note that the NRC says:
>'The International Commission on Radiation Protection, ... believes
>that, in the absence of convicing evidence that there is a dose
>threshold or that low levels of radiation are beneficial, the
>assumptions regarding a linear nonthreshold dose - effect model for
>cancers and genetic effects and the existence of threshold only for
>certain nonstochastic effects remain appropriate for formulating
>radiation protection standards.'" "Is that statement an accurate
>representation of the ICRP position?" Charlie answered, "Yes."
>
>So -- until there is "convincing evidence", that Charlie didn't define,
>it appears that the LH will continue to be the ICRP model. What we need
>now is a dialog with the ICRP to determine what constitutes "convincing
>evidence." It may be that such evidence can never be obtained.
>Therefore, those espousing a non-LH model may have their work cut out
>for them. Personally, I am no longer willing to permit such a
>conservative stance vis-a-vis radiation protection standards. It costs
>too much for no observable benefit.
>
>What evidence can we develop that will be convincing, not for the ICRP
>necessarily, but for the US regulatory agencies, so that we can get rid
>of ALARA at rediculously low doses, and collective dose? Would you be
>willing to join an organization set up specifically to eliminate the LH
>as the basis for radiation protection standards in the US? If so, please
>let me know. Al Tschaeche email: xat@inel.gov phone 208-526-3383, fax:
>208-526-7291, address: LITCO P.O. Box 1625, Idaho Falls ID 83415-3406.
>
>*** Reply to note of 10/16/95 07:01
>
>From: Wesley M. Dunn
>To: RADSAFE --INELMAIL RADSAFE
>
>Subject: Re: linear hypothesis
>
>Alex makes several good points in his note.  I would like to add
>another comment or two:
>
>1) This is =radsafe=, not a discussion among members of the public.
>The open discussion discussions that belong here are not necessarily
>the same ones we would give members of the public (where the HP is
>"The Expert", as opposed to one of several able to give an informed
>opinion).  HPs have historically placed a hoard of caveats on any
>statements made to non-HPs. (This also responds to Rich's earlier
>"ethics" note)
>
>2) The linear-no-threshold model is a MODEL and a HYPOTHESIS.  It
>may be true.  It may not be true.  It certainly has not been proven.
>One might question whether it is even a consensus opinion AT LOW
>DOSES.  (Sorry for the bold, but mailers don't do fonts very well)
>
>Wes
>
>> Date:          Mon, 16 Oct 95 00:13:04 -0500
>> Reply-to:      radsafe@romulus.ehs.uiuc.edu
>> From:          a.zapantis@qut.edu.au (Alex Zapantis)
>> To:            Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
>> Subject:       linear hypothesis
>
>> As professional HPs, I believe that it is our responsibility to provide
>> advice based on the current accepted state of knowledge. Those of us who
>> quote individual studies which include the words "radiation hormesis" in
>> their conclusions as a basis for discrediting the linear model remind me of
>> the lobbyists who use certain studies into ELF health effects (and ignore
>> the majority) to attempt to stop the erection of transmission lines in their
>> suburbs.
>
>*********************************************************************
>Wesley M. Dunn, C.H.P., Administrator      512-834-6688
>Licensing Branch                           512-834-6690 (fax)
>(Texas) Bureau of Radiation Control        wdunn@brc1.tdh.state.tx.us
>*********************************************************************
Reply:

For what it is worth, the HPS is indeed in the final stages of a position
statement on Linear-No-Threshold Model.

It is one thing to have a model and another to have validated it under all
conditions.  While it may be conservative for purposes of radiation
protection, it is not necessarily the complete summary of the scientific
facts.  For risk assessment one may wish to use a more realistic approach,
but to set regulations to abate a microsievert of dose requires some cost
justification based on harm averted.  One may never be able to answer this
epidemiologically, and we may be spinning our wheels to try to replace it
with a threshold or hormesis model.

What may be best for the interim, is an insistence of associated benefit
for such costs.  Where the costs do not make sense, perhaps the "linear
risk" will just be acceptable as perhaps an estimate of the upper bound of
the risk, since it is calculable but not measurable.  What we don't need at
the ANS, etc., is another screaming session where no one listens and we
just preach to the choir.

It may be that society is ready for some cool discussion of relative risks,
which are in less of a vacuum.  I don't mean to reinvent the wheel, just to
perhaps try to keep it in perspective.  Regardless of the "model", most of
these "micro" doses can probalby be considered of no social or medical
importance as long as they are recognized for what they are and not denied.
Am I dreaming about an age of reason?

Marvin Goldman