US NRC Press Release...Low Level Waste Forum,Panel on Radiation Health Effects...

[Mike Grissom <mikeg@SLAC.Stanford.EDU>]

Radsafers,

Commissioner Dicus essentially takes the LNT bull directly
by the horns, as it were, in the subject presentation.

Happy reading for those LNT warriors interested!

S.,

MikeG.

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The following may be viewed in its entirety (below is an
extract of a much longer document) on the Web at URL:

	http://www.nrc.gov/OPA/gmo/nrarcv/s98-07.htm

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Nuclear Regulatory Commission
Office of Public Affairs
Washington DC 20555
Telephone: 301/415-8200 -- E-mail: opa@nrc.gov
S-98-07

                  Greta Joy Dicus, Commissioner
               U.S. Nuclear Regulatory Commission
                             at the
           Winter Meeting of the Low Level Waste Forum,
                Panel on Radiation Health Effects
                      San Diego, California

                       February 10-13, 1998

                           INTRODUCTION

Let me start by expressing my appreciation for being invited to
participate in this meeting. Low level radioactive waste disposal
continues to be a major National issue and the Low Level Waste
Forum provides an excellent vehicle for focussing attention on
current issues.

As many of you are well aware, my experience includes serving
first, as member of the Central Interstate Low Level Waste Compact
Commission, and then as its Chairman. Thus, upon becoming an NRC
Commissioner, I had the opportunity to view low level radioactive
waste issues from the State and Compact perspective and now I view
the issues from a National and even international perspective.

However, in my remarks today, I will not focus on specific waste
issues but rather on an overarching issue with implications for
decisions regarding waste generation, management and disposal.
This overarching issue is the health effects of exposure to low
doses of radiation or low dose rates and the associated concerns
regarding standards setting and regulatory decisions.

Most discussions of radiation health effects will include comments
about the basic model underlying most radiation protection
standards - the linear, non-threshold (LNT) theory. More
specifically, the comments may center on the controversy
surrounding the theory.

So, this morning, in keeping with the overall purpose of this
panel, I would like to speak briefly about the controversy over
the linear, non-threshold theory for radiation health effects, in
particular, why there is a controversy, and what could be done to
help resolve the controversy.

As you know, the bulk of our knowledge about human radiation
health effect that forms the basis for radiation protection
standards is derived from studies of the survivors of the atomic
bombs that struck Hiroshima and Nagasaki. Other human population
groups that have provided significant data on radiation health
effects are certain medical patient groups. It is largely the
result of these human studies coupled with research on radiation
effects on animals and cells that have led to the adoption on
the linear, non-threshold (LNT) theory to describe radiation health
effects at the low doses and dose rates normally encountered by
radiation workers and the public. The strict application of that
theory at these low levels is being challenged. The reasons for
the challenge are complex. In the opinion of some, the strict
application of the LNT theory has lead to unnecessarily
conservative radiation protection standards particularly for
specific purposes such as the decontamination and decommissioning
of licensed facilities. As we will see, there is scientific
uncertainty about radiation health effects at these low levels.
Thus, one way of obtaining relief from radiation protection
standards that are viewed as unnecessarily restrictive or overly
conservative, is to challenge the theory underlying the standards.

                  IAEA INTERNATIONAL CONFERENCE
                      ON LOW LEVEL RADIATION

This issue has attained international attention. The International
Atomic Energy Agency (IAEA) and the World Health Organization (WHO)
sponsored an international conference which was held last November
in Seville, Spain. The conference title was, "Low Doses of
Ionizing Radiation: Biological Effects and Regulatory Control."
More than 600 persons registered for this meeting and I would like
to share some observations from it that I believe you will find
are relevant to this panel's topic. It was the first time that
scientists and regulators have met to jointly discuss the issue.

The conference was also held in cooperation with the United
Nations Scientific Committee on the Effects of Atomic Radiation
(UNSCEAR). In its first announcement of the meeting the sponsors
stated:

"The levels and biological effects resulting from exposure to
ionizing radiation are continuously reviewed by [UNSCEAR]. Since
its creation in 1928, the International Commission on Radiological
Protection (ICRP) has published recommendations on protection
against ionizing radiation. These recommendations have served as
the basis for national, regional and international safety
standards on this matter, including those developed by the IAEA
and the WHO...

The biological estimates of health effects of low doses of ionizing
radiation and the regulatory approach to the control of low level
radiation exposure have both been much debated during recent
times....The time therefore seems appropriate to take stock of
these new advances [in knowledge] and to identify areas towards
which new or greater research and development effort might best be
directed."

The Seville conference featured two background sessions for
reports on developments and findings in the radiation protection
field and ten fora on specific aspects of radiation effects and
control measures.  A special session entitled, "From the
Scientific Evidence to Radiation Protection" was interspersed in
the fora and provided a transition from sessions on biological
effects to those addressing regulatory control. The schedule
concluded with a round table on regulatory control and scientific
research, a conference summary session and closing of the
conference. The conference was opened by Hans Blix, IAEA Director
General who noted that this was the last IAEA conference he would
open prior to his retirement and by Dr. Hiroshi Nakajima, WHO
Director General.

A variety of views were expressed during the course of this
conference but the discussions did not lead to putting to bed the
current controversies over the appropriateness of using the
linear, non-threshold (LNT) model that underlies present ICRP
recommendations and regulatory radiation protection programs. U.S.
trade press articles, to a great degree, captured the spirit of
the debates. See Nucleonic Week, November 20 & 27 and December 4
1997 and Inside NRC, Nov. 24 1997.

In a nutshell, there are uncertainties about the radiation health
effects that are associated with the radiation dose and dose rate
levels that we regulate. With the possible exception of fetal
radiation effects, radiation health effects in humans at these
low levels have not been demonstrated. The critical assumption
made for creating a radiation protection system is that there is
a linear, non-threshold relationship between radiation and health
effects at low doses and dose rates. There is some evidence of a
threshold and possibly for hormesis for selected biological media
and radiation effects. But such evidence, frankly, must become
overwhelming and be demonstrated in humans before there will be
serious consideration to moving away from the current LNT
assumptions that underlie the present radiation protection
framework. Further, while their views are not widely accepted,
there are also scientists who believe that there is evidence that
radiation health effects at low doses and dose rates are
underestimated by the LNT assumption.

While no consensus was reached at the end of the Seville
conference, the prevailing view was probably best expressed by Dr.
Sheldon Wolff of the Radiation Effects Research Foundation who
said in the closing session that data on hormesis effects must be
convincingly positive before changes to theories underlying
radiation protection recommendations could be made, otherwise, "we
are dealing with religion, not science." The comment drew applause
from many in the audience.

...

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