Low doses (was Re: HPS objectives)

[David Scherer <scherer@uiuc.edu>]

David Lee wrote, in part:

>Thus a question back to David Scherer:  How low-level must the exposure
>rate or dose be before you declare an "unnecessary" exposure to be so
>trivial as to not concern yourself with it anymore?

Just because I pose the question, do I have to have an answer? :^)

The whole point of my posts is that there is no unique answer to this
question.  The question asks about values, not science.  My scientific
training has not equipped me to address this question.  How has society
assigned responsibility in the past when the risks were uncertain?  Even
more important, what is the rationale for assigning this responsibility?
This may be heretical, but I don't believe HPs have any greater standing
than other members of the public in addressing these questions.

Dave suggests a multiple of background, claiming there is no health defect
from background.  I would ask how he knows there is no health defect.  We
can say that no health consequence have been detected given our statistical
tools.  That's what the LNT debate is about.  Are you saying you have
conclusive evidence of a threshold at a certain dose?  I personally would
be very happy to learn that there is an absolute threshold at some given
dose, but I believe a defensible number for that value is not available at
present.

You pick a value of 2 or 3 times background.  Why is this better than 1/3
background (NRC limit for the public)?  You pick this by some tradeoff in
your mind.  That's what we should discuss: not the numerical limit, but the
reasoning behind this limit or that.  Don't get me wrong.  I personally do
not advocate chasing every last millirem.  (For example, we don't give
whole body badges to people performing bench top chemistry.)  It is pretty
clear to me when doses are trivial (mrem) and when they are not (rem).  It
is ground in between that I find difficult.  If people talk about the basis
for a limit, especially the tradeoff in values that is involved, maybe
we'll get a littler closer to agreement.

Since you mention background, I would like to respond to a comment I have
heard in several forms.  We require employers to measure and control
exposures from their operations even if it is less than or comparable to
background.  Sometimes people say that this is because we view background
as "good" radiation while occupational exposure is "bad."  I would suggest
that the reason we treat them differently turns on responsibility.  The
employer is responsible for the workplace, not for Mother Nature.  No
matter what exposures nature gives, the employer is still responsible for
his addition.  Radiation standards are not graded on a curve.

I will be out of the office for a week (loud cheers from radsafe land) but
I'll be interested to read your comments when I get back.

Dave Scherer
scherer@uiuc.edu