NRPB's "Second Event" Theory
Report from Radioactive Times Volume 4, Number 1, June 2000 (content not updated)
Time for the theorising to stop: this issue can only be addressed adequately by experiment.
As we reported in Radioactive Times Volume 3, Number 1 (March 1999) NRPB's Dr Roger Cox undertook, during a meeting with LLRC and Environment Minister Michael Meacher, to help get the Second Event theory published in the peer-reviewed literature. [link to Cox's version]
Dr Chris Busby's Second Event theory proposes a mechanism of genetic mutation at extremely low doses of radiation when cells' genetic repair cycles are interrupted and subverted by sequential radiation tracks (or "second events") from hot particles and some man-made isotopes which decay more than once. Busby published it in Wings of Death after it had been excluded from the International Journal of Radiation Biology (IJRB) on erroneous grounds in 1992 1.
The Second Event theory has been widely discussed, but publication in peer-reviewed journals is conventionally seen as indispensable if new scientific ideas are to be debated, and Busby's critics have been quick to attack on the grounds of his exclusion from the literature. Now, in a bizarre reversal of the way peer reviewed journals usually conduct scientific debate, the IJRB has published a "Commentary" on the theory by NRPB'S Drs Cox and Edwards 2.
Reworking Busby's most recent calculations using Strontium-90 as an example, but using different data for the number of cells potentially exposed to radiation tracks from any given atom, they find that the chances that a cell would be hit by two events from the Strontium decays are hardly any greater than the chances of being hit twice by natural background radiation.
Responding, Busby observes that by Cox and Edwards' own calculation the existence of one atom of radioactive Strontium within an individual cell is, as far as that cell is concerned, equivalent to doubling the external natural background exposure to the whole person. It is unethical to write this off as trivial, he says. It is like arguing that I may hit my neighbour with a piece of wood (a crime) if he has already suffered from a tree falling on him as a result of a gale (an act of God).
He adds that NRPB has failed to take account of other sequentially decaying isotopes like Tellurium-132 which present an even greater hazard than Strontium, and hot particles of Plutonium and Uranium Oxides which are widely distributed in the environment. It is easy to show that the 0.1 micron range 239Pu particles will deliver infinitely repeated decays with about the right timing to set up and then knock down the cell repair/replication process over and over again.
Hot particles of Plutonium and anthropogenic Uranium are found in estuarine silts in the Irish Sea and plutonium from Sellafield has been found across the whole country.
Busby welcomes the publication of Cox and Edwards' paper since it raises the question of the plausibility of an idea which may explain a number of epidemiological findings of excess cancer risk following exposure to internal man-made radionuclides. He points out that so far he and NRPB have been arguing over the validity of mathematical models.
While this is interesting, he feels, This issue can only be addressed adequately by experiment.
LLRC notes that although Cox and Edwards maintain stoutly that Busby is wrong, they seem to be tiptoeing away from NRPB's traditional defence of average dose.... at low doses of internal and external radiations, they write, risk is simply proportional to dose to target cells which ... is the conventional view in radiological protection.In fact risk is conventionally seen as proportional to dose to target tissue, which is a very different matter.
As LLRC has many times pointed out, the protection agencies minimise the predicted effects of radiation at the microscopic level by averaging them across large volumes of tissue, most of which will be out of range of the radiation tracks. If dose to target cells were really being fully appreciated this Campaign would have no function. Its workers look forward hopefully to being redundant.
1 see "Wings of Death: Nuclear Pollution and Human Health" Chris Busby Green Audit, Aberystwyth 1995 ISBN: 1-897761-03-1 p. 200
2 EDWARDS, A. A. and COX, R., Commentary on the Second Event Theory of Busby IJRB 2000, Vol 76, No 1, 119-125
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