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ICRP: Free the Annals!

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Submitted by SE Frost, Frost & Frost Consultants
   Commenting as an individual
Document 2005 ICRP Recommendation
 
While the stated intent of the 2005 recommendations to simplify the radiation protection system is laudable, I do not think that this has been achieved. The Commission states that there are no major problems with the practical use of the present system and, further, gives evidence that radiation risk is actually less than stated in ICRP 60, but still gives greater emphasis to a system of dose constraints that are more restrictive than the previously recommended dose limits. These constraints are certain to be interpreted as limits by the public and are likely to result in stricter regulations being applied to the use of radiation and radioactive materials. The current system would appear to be working reasonably well in most countries. If the risks are lower than previously thought, why recommend stricter controls?

I was disappointed to see no change in the radiation weighting factor for alpha particles. Some 25 years ago, Dr. CG Stewart, then Chairman of the ICRP Main Commission, who had devoted a great deal of study to uranium miners’ epidemiology, had suggested that the wRá was too high. When the 1990 recommendations were published, the wRá was again questioned and it was suggested that wRá= 20 was unlikely to be appropriate in all circumstances. This value is most soundly based in bone dosimetry and the production of bone sarcomas. Since miners’ lung cancers involve a very different tissue and a different cancer type, there is no reason to believe that the wRá should be the same.

The confirmation of wRá= 20 in the 2005 recommendations caused me to review the consideration of wRá in ICRP Publication 92. I noted a reference to PRJ Burchall and AC James in support of wRá= 20. Upon investigation I found that the reference should have been A. Birchall and AC James, and by happy coincidence I was present when the paper was presented and discussed. Contrary to what was stated in ICRP 92, Birchall and James did not support the use wRá= 20 but concluded that wRá was too high and DDREF=2 was too low (or at least that the combination wRá/DDREF was too high). In the discussion, which was reproduced in Radiation Protection Dosimetry Volume 53, pages 144-145, additional support was offered for a lower value of wRá for lung dosimetry. Clearly those drafting ICRP 92 did not give sufficient attention to their supporting documentation. This leads me to suggest once more that you reconsider the radiation weighting factor for alpha particles, in particular for use in lung dosimetry.

Using natural background as a basis for establishing dose constraints has some appeal as a means of explaining radiation protection standards to the general public. However, the implication that any doses above (a very low) background carry risk that demands attention is bound to continue to cause problems for nuclear power and other uses of radioactivity. The new system is basically recommending the control of doses below the range in natural background. People do not regulate their lives based on local background radiation. If they did, they would not take ski holidays in the mountains or long airplane flights. Yet these recommendations are suggesting that comparable and lower doses arising from such activities as nuclear power result in risks that require attention.

The linear non-threshold hypothesis is a convenient means of establishing conservative radiation protection standards, but it should be clearly stated that this does not reflect the true nature of radiation risk at low doses. Studies continue to fail to demonstrate any risk from radiation doses of a few tens of mSv. Many studies show stimulatory effects from low doses, which is in line with the effects of low doses of other toxic agents. Suggesting dose constraints as low as 1 mSv will continue the waste of resources on radiation protection that could better be spent on more serious problems.

I fully support the view that low individual doses should not be integrated over very large populations into the far distant future. However, suggesting that best available technology be used to control emissions to the environment does nothing to solve the problem.

Introducing the protection of the environment into the system is going to require much more careful consideration. For example, how does one optimise protection for humans and benthic invertebrates? The environmental aspects have the potential to consume a huge amount of effort that could be better spent in other areas.

In summary, the use of radiation and radioactive materials has had great benefits to mankind and has the potential to continue to offer great benefits. We must be very careful in framing radiation protection systems that we do not raise public anxieties to the extent that future generations will be denied these benefits.