Re: LNT and Public Fear

[John Goldsmith <gjohn@bgumail.bgu.ac.il>]

Dear Mark:
     While I agree with your conclusion and much of your logic, I must,
as an epidemiologist, deny that epidemiological observations are the 
sources of thresholds for hazardous chemicals or carcinogens.  It is 
experimental work that allows, under the circumstances of the experiment,
the statement that a threshold has been established.  Population variability
in responsiveness is the major logical reason for epidemiology being 
unable to establish a threshold.  Epidemiologic observations often can 
affirm that in a comparable population to the one studied, effects will occur 
at a given level of exposure, but it can never show that no unfavorable 
effects will occur below a given exposure level. (Which is what I 
understand a threshold to mean).  Finally, epidemiology can, under some 
circumstances, estimate the dose or exposure which would be associated 
with a lifetime increased incidence of a small number of cases, say 2-4 
per million.  In my view, at least, thresholds can only be based on 
epxperimental exposures, and are valid for sufficiently similar exposures;
it follows that experimental exposure of human populations to radiation 
are fraught with ethical problems, hence, thresholds for such exposure 
are not feasible.
    gjohn@bgumail.bgu.ac.il   John Goldsmith, M.D., Professor of Epidemilogy,
                              Ben Gurion University of the Negev
On Sun, 13 Oct 1996 MarkH@MAIL.KIDS.USYD.EDU.AU wrote:

> Friends, 
> 
> I feel that Dave Scherer's thoughts are on the right track.   
> 
> As in the case of hazardous chemicals and/or carcinogens, a "threshold"
> will be determined from epidemiological observations (i.e. of populations).
> The risk threshold therefore applies to the population, and cannot directly
> be applied to the individual. How many members of the public will
> appreciate this subtlety ? 
> 
> I suspect that, were a threshold introduced, many members of the public
> would still reason along the lines : "if 20 units is not safe, then can 10 units
> be completely safe ?".  (I guess this might not be the case if there were
> orders of magnitude of difference between the threshold and the typical
> exposure.) 
> 
> The real solution lies in educating the public.
> 
> 
> Mark Hanlon,
> Radiation Safety Officer,
> The New Children's Hospital,
> P.O. Box 3515,
> PARRAMATTA, NSW, 2124
> Australia
> 
> 
>