Re: Linear Hypothesis IS the Cause of P -Reply

[Joyce Davis <JOYCED@DNFSB.GOV>]

A few thoughts (opinion) in response to Al Tschaeche's latest posting
and this thread in general.
  If we set a purely threshold limit, the public, suspicious of
government, scientists, institutions, etc., will ask.  What happens
below the threshold?  How do you know?  Prove it?  For those of us
(i.e., those scientifically knowledgeable) who are convinced that
there are no, or possibly beneficial, effects below 5 rem/yr, the
answers are:  Nothing bad.  I'm convinced as a scientist.  Citations
to the literature.  But some of us (same definition) can only say "I
don't know  - but I'm convinced the bad effect, if any, is small"
(citations to the literature).  Alas, many in the public (e.g., those
who play the lottery because "someone has to win; it could be me")
will not be convinced.  "Some scientists say there might be a bad
effect".  To the risk averse this translates to:  "There may be a bad
effect; someone has to be damaged; it could be me; I don't want
that".
   If the LNT is seen as giving an upper limit on risk, I think it
can be helpful in at least defining to the public how "small" the
largest  "small" effect is.  If we leave people with the idea that
the effects of radiation, a menace undetectable to the senses, are
"unknown", we leave the door open for all sorts of monsters to enter.
     By putting an upper limit on the risk with the LNT assumption we
can at least hope to stop the idea that there may be a major
undiscovered effect lurking at very low doses.  (There are people who
believe that very dilute medicines are more powerful than
concentrated ones!).
    In short, at the present time (convince me otherwise), I think
the LNT is useful in 2 contexts: standards setting and establishing
an upper limit on quantified risk.  In other contexts, I think it is
more than useless; it is misleading, counterproductive, and all
things Al said about its influencing the demise of the rad world as
we know it. Quantitative risks derived from the LNT should NOT be
used in risk assessments that purport to show what the actual effects
of some radiation-producing action on actual people are, have been,
or will be.
      As HPs and rad scientists, we should not let simplistic use be
made of risk extrapolations by those who put together NEPA
statements, PRAs, and similar public documents.  Make sure every risk
assessment has uncertainties stated.  Make it clear that the LNT
extrapolation is an upper limit only; the actual value is somewhere
below that; it may be zero, it may be an itsy bitsy (de minimis)
detriment; it may be a benefit (also small).
     Until we can get a better handle on the quantitative detriment
of low doses or prove to a reasonably high degree of certainty that
low doses have a zero or beneficial effect, I suggest we put our
efforts into ensuring that the right risk assessments be used in the
right manner, not in declaring one way of estimating risk verboten. 
And maybe, just maybe, the public will begin to understand a little
better.
    Don't you think that if the entire HP community, nuclear
industry, and regulatory agencies came out today for a threshold at 5
rem per year and a prohibition on the use of the LNT, many in the
public would interpret it, not as the triumph of reasonableness but
as another conspiracy of the power elite to make money at the expense
of the powerless citizen, exposed to invisible rays?

Only the opinion of  J. P. Davis
joyced@dnfsb.gov