The Harmful Fallacy of Collective Dose

Use of Collective Radiation Dose as a Measure of Good Practice or of Casualty Magnitude

This essay was written some time ago, but the history seems to need repeating, as people increasingly misuse cumulative or collective dose.  Adding up individual radiation doses is like adding up temperatures.  It gives a figure with no physical meaning. 

NRC uses as a prime measure of the severity of a casualty, or the efficacy of “good plant operation,”

the total collective radiation dose in person-rem, multiplying trivial individual radiation doses by large

numbers of people to “predict” many induced cancer deaths. That process has been repeatedly

condemned as scientifically indefensible. Yet current policy presumes that, in the absence of more data,

this is the prudent course. That contention is wrong on both counts: there is no lack of applicable credible

data and the data show persuasively that low-dose radiation is not harmful. And use of this unwarranted

practice continues to have serious detrimental effects.

NCRP-121 specifically warns that collective dose should not be used to predict death or injury from

low-dose radiation:

“The summation of trivial average risks over very large populations or time periods…has produced a

distorted image of risk, completely out of perspective with risks accepted every day, both voluntarily and

involuntarily.” (p.58)

And again:

“…it is recommended that regulatory limits not be set in terms of collective

dose…When the uncertainty in the number of individuals …is large… collective dose

should not be used as a surrogate for risk, even at relatively high levels of individual

radiation dose.” (p. 62)

Roger Clarke, Chairman of the International Commission on Radiological Protection wrote (1 Oct 98

at http://hps.org/documents/controllable.pdf) :

“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”.

And the Health Physics Society, in its March 1993 Position Statement, emphasized in bold-faced type:

“We strongly recommend that dose limits be applied only (sic) to individual members

of the public, not (sic) to the collective dose to population groups.”

The French Academy of Medicine quoted and concurred with the above statement from NCRP-

136, and stated in a press release 4 Dec 01:

[the Academy] associates with many international institutions to denounce improper

utilization of the concept of the collective dose to this end. These procedures are without

any scientific validity, even if they appear be convenient to administrative ends.

Zbigniew Jaworowski, MD, PhD, the noted member and former chair of UNSCEAR, wrote in

“Radiation Risk and Ethics” (Physics Today, Sept 1999, 24-29) that use of collective dose:

“was introduced in the early 1960s…the concept is still widely used, although both

the concept and the concern [about harmful hereditary effects] ought to have faded

into oblivion by now…Individual doses cannot be additive over generations, simply

because humans are mortal and the dose dies when an individual does. Similarly,

individual doses cannot be added for individuals of the same generation because

we do not contaminate one another with a dose that we have absorbed…

If harm to the individual is trivial, then the total harm to members of his or her

society over all past or future time must also be trivial—regardless of how many

people are or will have been exposed…

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