Re: linear hypothesis

[psr@po.CWRU.Edu (P S. Rao)]

The Linear-No-Threshold hypothesis never fails to arouse strong
passions.  Echoing Dr. Goldman's comments, I wish to emphasize
that there are two separate issues.

One is the validity of the hypothesis.  Proving or disproving it
falls in the domain of radiation physics, radiation biology, and
biostatistics, all in about equal proportions.  As pointed out in
earlier radsafe submissions, it will be next to impossible to
achieve the huge number of observations required for a
categorical proof one way or the other.  Nevertheless it is a
fertile area for inquiring minds to probe and ponder.  Without
such topics, health physics would be quite dull.

The second is the practical necessity to choose the assumptions
on which to base the policies and procedures for using radiation. 
The questions to ask are:  "What are acceptable levels of risk
for occupational workers and the public?  How should those risks
be related to dose in rems?"

I agree with those who would base risk assessment on observable
effects.  The HPS Position Statement published in the August
issue of the HPS Newsletter should be pursued more aggressively. 
The cost-benefit ratio in radiation management should be
comparable to that in other hazard management schemes.  Basing
regulations on presumed or theoretical effects from
millirem/microsievert levels is scientifically questionable, as
even the NRC (bless their souls!) recognized when they tried to
promote BRC.

The problem will ultimately be with the lay public, which has
been led to believe that all radiation in any quantity and any
form is dangerous, and which is pandered to by sensation-seeking
news media and vote-seeking legislators.  Until the public has
been better informed about the known and observable effects of
radiation, there may be litle hope for ratcheting action levels
back from the millirem/microsievert range to the rem/mSv range.

--
P. Sridhar Rao, Radiology, CWRU / Univ Hosp of Cleveland, Cleveland, Ohio.
Tel: 216-844-1295.    Fax: 216-844-5922.    E-mail: psr@po.cwru.edu