March/April 1995 Issue #32

The Chernobyl Risk and Health Effects Debate:
Using Risk Assessment Criteria to Deny Risk

The following excerpts are from a presentation by Abel Gonzalez, Deputy Director of Nuclear Safety for the International Atomic Energy Agency, and from a question and answer exchange he had with a member of the audience at the Atlanta meeting of the AAAS. These excerpts are presented to illustrate how the highly selective use of burden of proof criteria by scientists involved in environmental risk assessment can result in the denial of any risk. All statements are from tapes of discussions, provided by the AAAS, or from the printed text from which Mr. Gonzales made his formal presentation.

Mr. Gonzales' introduction: "Hesitation seems to exist world wide with regard to activities involving Chernobyl Risk Debate, radiation and radioactive materials, and in particular towards using nuclear power as an alternative source of energy. Public perception of the effects of radiation is the root cause that, directly or indirectly, has negative effects on the acceptance of these activities.... Although the public perception is different, the levels of radiation exposure and the biological effects associated with them are well known and they certainly do not represent a health concern."

Definition of deterministic and stochastic effects of radiation: "Deterministic effects result from the killing of cells which, if the dose is large enough, causes sufficient cell loss to impair the function of the tissue..... For deterministic effects, assuming that the effect is reliably diagnosed, causality is always certain. Deterministic effects are uniquely caused by radiation exposure; they occur in a short time after the radiation. . . . Stochastic effects may develop a long time after an irradiated cell is modified rather than killed. For stochastic effects, on the contrary, causality is never certain in individual terms. . .The cause-effect linkage can be established only for populations as a whole, and even in this case the relation is uncertain."

On the stochastic projection of cancer rates for low dose radiation exposure: " ..the probability being an order of five per hundred thousand per mSv (millisevert, measure of radiation dose) for a working population and around seven per hundred thousand per mSv for the general population."

Question by Richard L. Garwin, Fellow Emeritus, IBM Research Center, based upon Gonzales' figures for projection of cancer rates.

" In your twenty three page paper I missed an important conclusion. And I wonder if you will agree as it can be drawn directly from your numbers. You say that the International Advisory Committee says that the total world wide dose to people is 600 Sv. You also say that there is a five/hundred thousand [sic] incidence of cancer predicted. Multiplying those two I gather that there will be 30,000 cancer deaths among the world population due to Chernobyl if we believe those numbers. Within the former Soviet Union the corresponding calculation will be 12,000. Do you agree with that conclusion?"

Response of Gonzales: "This is a trap, and I will tell you why. It's a trap because that number is a conservative number developed for radiation protection purposes. But we have been unable to experimentally prove that number. There are many people who believe that after the initial effect of radiation upon on the cells, the [human body] has repair mechanisms much more effective than we thought. An UNSCEAR (United Nations Scientific Committee on the Effects of Radiation) study, called "Adaptive Response," showed clearly that a cell has a repair mechanism that is more and more and more efficient as radiation goes up. Therefore we do not know with certainty. I am O.K. using that number for design purposes. . . But to use that number to estimate that 30,000 people have died, that I have not seen, that I cannot detect, is really a trap. Maybe it is true, maybe it is not. It is irresponsible to say, with absolute certainty, that 30,000 people have died. I cannot measure it. I can not establish causation for this."

Gonzales on the topic of public perception of radiation risk: "Contrary to what facts seem to indicate, public perception of radiation exposure is that it has devastating health consequences. It is difficult to understand such a wide gorge between the objective scientific information and the actual perception of it... Or is it just self-interest (very nice but not in my backyard, please!)"

On the health effects of the 1986 Chernobyl accident: "The UNSCEAR assessment shows that on a global scale, the total radiological impact of Chernobyl has been minor in technical terms. This amount is about five percent of the global collective dose delivered by natural sources each year."

Summarizing the findings of the International Chernobyl Project: "no health disorders were detected in the affected population that could be directly attributed to radiation exposure. . . .Thirty workers died and two hundred were overexposed."

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