Re: Controllable Dose, Roger Clarke, 1 Oct. 1998

["Sandy Perle" <sandyfl@earthlink.net>]

> Prof Clarke's concept is very persuasive and has some unique features.

It is these unique features that I take issue with. For example:

(1) Dr. Clarke states "It does not apply to exposures that are not 
amenable to control, such as cosmic radiation at ground level, but 
would apply to high terrestrial levels of natural background." My 
question is how does one regulate this, and, do we make individuals 
move solely for the reason that they are exposed to high levels of 
natural exposure, that does not originate from cosmic radiation?

(2) "The significance of a level of controllable dose depends on its 
magnitude, the benefit to that individual and the ease of reducing or 
preventing the dose." This is essentially ALARA. Mandating ALARA 
levels was attempted in the USA, and was dropped from the 
regulations. The only reference now is that there must be a program, 
but there are no prescriptive level requirements stated. Each 
situation must be assessed on its own merits. There are too many 
variables in this consideration; 1st the risk, 2nd the benefit and 
3rd the ability to reduce. We all know the consequences of having too 
many variables to manage.

(3) "If the risk of harm to the health of the most exposed individual 
is trivial, then the total risk is trivial - irrespective of how many 
people are exposed." I fully concur with this statement.

(4) Dr. Clarke lists various dose limits, i.e., 20 mSv/year 
occupational dose, 10 mSv/year from home radon, tens of mSv per 
medical procedure, such as a CT scan."While these levels of dose to 
the individual can hardly be called unacceptable, they are levels at 
which questions should be asked as to whether the dose and associated 
fatal risk which will be of the order of 10^-3, or 1 in 1000, can be 
avoided by some sort of action." This seems to come down to whether 
or not LNT is a valid concept or not. My own personal opinion is that 
the evidence today suggests that Dr. Clarke's concept is even more 
restrictive, and conservative, than the current regulations and 
recommendations, and yet there is no evidence that dictates that we 
need to decrease any dose limits. In fact, we should increase the 
regulatory limits, not lower them, based on the evidence that does 
exist today.

(5) ".. a single "limit" of controllable dose. The value would be 
around 20-30 mSv in a year." Again I come back to how does one 
document the varying components that make up the controllable dose 
that is assigned to the worker, or, the general public. We have good 
details on the occupational dose. How do we capture all of the other 
dose components. While it's nice to propose a new method of 
accounting, the process needs to be defines. Not every entity is 
sophisticated enough to do all of these measurements and 
calculations.

(6) "(a) what quantity is to be used to assure that the source 
provides an overall benefit from its introduction, and (b) how is 
"asl low as reasonably achievable" to be judged when individual dose 
is the determining criterion." What mechanism is the benefit to be 
documented. From medical applications, there is an obvious answer. In 
some cases, it's obvious, as with power reactor employees, research, 
etc. If one must justify all dose by benefit, including natural 
sources, this will be very difficult.

In conclusion, in my opinion, Dr. Clarke's proposal will do great 
harm, not provide any real benefit in the way of reducing individual 
ailments or reduce any loss of life. In fact, reducing the limits to, 
and including all of the factors considered would actually do more 
harm to the general public, and to the occupational workers. For 
example, if the individual dose limit is lowered, the work still must 
be accomplished. Therefore, additional workers will be required. This 
is a direct contradiction of the concept, that being the dose to the 
individual being paramount, and not the collective dose. Here we 
could actually increase the number of exposed individuals.

I hope this proposal never sees the light of day, unless modified 
considerably.





------------------------------------------------------------------------
Sandy Perle					Tel:(714) 545-0100 / (800) 548-5100   				    	
Director, Technical				Extension 2306 				     	
ICN Worldwide Dosimetry Division		Fax:(714) 668-3149 	                   		    
ICN Biomedicals, Inc.				E-Mail: sandyfl@earthlink.net 				                           
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Personal Website:  http://www.geocities.com/capecanaveral/1205
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