LNT,cabbages and kings

[Bill Prestwich <prestwic@mcmaster.ca>]

Dear Radsafers

 I think there is a mixture of issues confusing the current LNT debate,

some of which have

been alluded to. Firstly, there is the scientific question-what is the

response of a human being to

ionizing radiation? Secondly there is the question of whether or not

current regulatory practice is

appropriate. And finally, there is the impression that society has of

the situation, which has very

broad consequences. I would like to start with the last. I have seen in

print and heard in

commentaries etc many times the statement .Science has shown that there

is no safe level of

radiation., expressed in various alternative forms with identical

thrust. I can only conclude that

this claim is an expression of a common interpretation of the LNT

hypothesis. Of course, the

response that the use is only for regulatory purposes, and no one is

saying that the LNT is

scientifically proven may be technically correct, but is practically

ineffective. The Orwellian

consequence of the continual repetition of this misuse of reality is

that it has become

indoctrinated as a truism-indeed a case of perception being reality. The

consequence has been a

distortion of our practices to accommodate an exaggerated sense of

potential harm. The root

problem however is not only the misuse of the LNT, but the much more

important distortion that

claims there is a scientific definition of the word safe, and that that

definition is a procedure with

zero associated risk. With this mind set for example, it is entirely

possible that a scientific

demonstration of a threshold could leave us worse off than with the LNT

model. Suppose the

threshold was observed at a dose much lower than we commonly deal with.

I firmly believe there

would then be enormous political and societal pressure to make the

threshold a de facto

regulatory limit.

 As has been pointed out regarding the first question, it seems likely

that at least through

epidemiological studies with finite populations that we will never

completely determine the

response down to the origin. Nevertheless, based upon current science we

can I think establish a

reasonable upper limit to the risk for doses below a certain value,

which is virtually model

independent. What is missing however is an acceptable consensus on a

reasonable assignment of

a risk level that should be considered .equivalent to the word safe.

 The argument that regulatory use of the LNT is justified on the basis

of prudence is not

entirely acceptable. This is because, according to the current joint

societal model of the LNT and

safe as zero risk, it is possible to interpret current regulatory

practice as declaring the act of

drinking a glass of milk, eating a banana etc is unsafe because of the

increased radiation

exposure. I am sure that great former president Harry Truman would react

to this situation with

his usual polite epithet of horse manure.

 So I think that the real tragedy has been the defeat of the proposed

concept of Below

Regulatory Concern from the technical point of view, and more broadly

the unwillingness to

claim that for all practical purposes there is a safe level of

radiation.

Sincerely,

Bill Prestwich





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