Re: radsafe posts

[David Scherer <scherer@uiuc.edu>]

Jim:

Dose Equivalent:  We use DE in radiation protection as part of our effort to
control worker exposures.  As I mentioned earlier, we could keep records of
each type of exposure and develop some formula for looking at a combined
risk.  This would be quite complex without achieving any added safety.
Instead, we combine occupational exposures of different radiation types
using the DE.  This can be useful even if the Q values are subjective.
After all, they are essentially safety factors.  When a structural engineer
designs a bridge, there is no objective, scientific method for selecting the
safety factor she will incorporate in the design.  A design basis is
selected based on the compressive strength of concrete AND an arbitrary,
perhaps unknown, safety factor added.  I'm not going to demand that bridges
be built only to the design basis!

The problem comes in when we use DE in radiobiological or emidemiological
experiments.  So we calculate DE for radium or radon exposures using Q with
all these safety factors.  Of course we don't see cancers associated with
radium or radon exposures.  In the structural analogy: suppose a bridge is
designed to hold a 10 ton load plus added safety factor(s).  The engineers
want to test the theory so they drive a 10 ton truck onto the bridge.  The
bridge does not crumble, so the engineers conclude the compressive strength
of concrete is not accurately known!

Public Perceptions:  I disagree with you that public fear is caused by the
linear model.  People are concerned about NOx levels in drinking water even
when they are far below EPA standards.  The public does not feel safe
because they use a threshold model.  Also, the statement that "No dose level
is absolutely safe" does not cause the fear.  People are averse to normal,
municipal landfills, even when no such statements apply.  Instead, people
are afraid of the unknown, especially the high tech, manmade, unknown.  The
aversion is compounded when they have no control over the matter, even if it
is not especially hazardous.

I don't think public perception would be substantially altered if a
threshold model were adopted by some scientific group or regulatory agency.
In my experience people's attitudes are changed when they understand that
radiation is natural, not manmade.  Most people can put the risks in
perspective when they learn that they are exposed to about 100 mrem per year
from natural, external radiation and an additional 200 mrem "equivalent"
exposure per year from radon.  Then they seem to recognize that an
additional 10-100 mrem from their work, etc. is truly trivial.

Regards,
Dave Scherer
scherer@uiuc.edu