LETTER TO THE EDITOR

 

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It was interesting to see in Journal of Radiological Protection volume 20, issue 1, a scientific journal so full of non-science judgements, with consideration being given to the societal impact of very small doses and the sum of these, the collective dose. The paper by Fairlie and Sumner (page 9) seemed to justify the use of collective dose on the grounds that everyone's doing it, so it must be OK. However, the authors only reached the nub of the argument in their very last paragraph and then unfortunately did not develop it.

The crux of the issue of the calculation of collective dose to assess the impact of radioactive discharges is, surely, that there is no standard or limit with which to compare the effect of such implied societal damage. If the LNT dose-response relationship is deemed to be reasonable we must accept that there will be an effect or health detriment (or whatever it is called) down to the lowest dose or discharge. As an industrialised society we must then judge whether we consider such cancers as acceptable or not - but this can't be done in isolation. All industrial discharges cause some harm and many are responsible for fatal cancers. It might be more appropriate if, for instance, the generation of electrical power was considered in terms of deaths/GW_e - it might be that the burning of coal and oil would not appear to be such a good idea even in comparison to nuclear power.

In one of the only attempts to use collective dose as a standard to limit discharges, the Swedish Radiation Protection Institute in 1987 made the telling point that the purpose of the assessment of collective dose is to '... obtain a measure of whether the harm which radiation can be expected to cause ... in comparison with other sources of energy, is justified'. They conclude that discharged chemicals from other industries could last forever in the environment but also that decisions over the justification of nuclear power generation based on the implications of collective dose are 'political' and therefore, presumably, outside scientific debate. There is clearly a dichotomy here with, for instance, the NGOs living in a simplistic world where all cancer is attributable to man's pollution of his environment, and the nuclear industry who are afraid to admit that their discharges into the environment will probably (or even actually) cause some cancers. Surely the answer cannot just revolve around the concept or implication of collective dose calculations?

Nevertheless, at the end of the day, I think the concept of collective dose is worth retaining, but with some caveats. It tells us nothing about distribution of dose which should be a problem even in optimisation situations. In addition, it must be understood that modelling doses from environment pollution over millennia and over vast areas is absurd and fairly meaningless. For instance, I find I must also agree with Roger Clarke when he suggests, effectively, that collective dose calculations are meaningful only when the individual doses are well established rather than vague extrapolations. However, the implications of the collective dose calculation focus attention on the real (industrialised) world and might just encourage comparative risk assessments which would be to the benefit of the environment and society.

 

Dates

Issue 3 ( 1 September 2000)