LNT versus threshold (formerly pound of plutonium)

[Andrew Karam <karam.1@osu.edu>]

Radsafers -

This is the text of e-mail I recently sent to Gen Roessler to consider for
inclusion in a future HPS newsletter.  Given the recent comments on
RadSafe, I thought it might be appropriate to post this here.

Andy
------------------------------------
In some practical respects, the debate between proponents of the LNT and
Threshold hypotheses may be moot.  Consider:

According to Cohen (1991), the risk from exposure to 1 mSv/yr for a
lifetime is about 1 in 10,000.  I have not heard many health physicist
argue vehemently against this dose limit for the general public, and I
suspect that many of us would feel comfortable with a limit of up to 4 or 5
mSv/yr.

Kondo (1993) noted studies showing apparent thresholds ranging from
non-existant to over 0.5 Sv.  In conversations with a number of respected
health physics researchers, I have heard many suggestions that a threshold
(or effective threshold) level of about 0.2-0.3 Sv is not unlikely.  Over a
70 year lifetime, this comes to about 4 mSv/yr.  

While the exact shape and slope of the radiation dose-response curve is of
great interest, perhaps we should agree to pursue different strategies
academically and practically.  From a more practical standpoint, perhaps we
can all agree that an exposure of 0.4 mSv/yr to the general public is
acceptable and harrangue our representatives accordingly.  

The academic debate over the exact nature of radiation dose-response is
important and needs to be resolved.  The results of this debate will let us
know exactly what sort of safety margin we have with whatever limits we end
up with.  But, from a practical standpoint, it could be that we all have
more in common than we think.

References:
Cohen, B.L., Catalog of risks extended and updated.  Health Phys. 61:317; 1991

Kondo, S., Health Effects of Low-level Radiation, Medical Physics
Publishing, 1993



The opinions expressed above are well-reasoned and insightful.  Needless to
say, they are not those of my employer. (with apologies to Michael Feldman)		

Andrew Karam, MS, CHP					(614) 292-1284 (phone)
The Ohio State University 					(614) 292-7002 (fax)
Office of Radiation Safety					"The mind is not a vessel to
1314 Kinnear Road						be filled but a fire to be
Columbus, OH  43212						lighted." (Plutarch)	   
(karam.1@osu.edu)