The scope of radiological protection

Draft document: The scope of radiological protection
Submitted by Eli Stern, Center for Risk Analysis, Gertner Inst f Epidemiology & Health Policy Research, Tel-Aviv University
Commenting on behalf of the organisation

Re: Comments on Building Materials Paragraph (6.3.1, subparagraphs 96 -102) in ICRP Draft Pub. "The Scope of Radiological Protection Regulations" (02/258/05 – spring 2006 Version) 1. With reference to my telephone conversation with Dr. Abel Gonzalez (of September 14) concerning the draft, and in accordance with his recommendation, I would like to convey to the ICRP Task Group a few preliminary comments regarding the limitation of exposures of members of the public and population at large from building materials. 2. Following the discussion of average worldwide exposure from building materials (0.4 mSv/y), with a typical range of 0.3 – 0.6 mSv/y and extreme exposures as high as several mSv/y (up to 10 mSv/y in certain houses in Europe), the TG draft document recommends, that the activity concentrations of K40, Ra226 and Th232 in building materials should comply with C K-40 / 10 Bq g-1 + C Ra-226 / 1 Bq g-1 + C Th-232 / 1 Bq g-1 < 1 This equation is based on IAEA's RS-G-1.7 Safety Guide exemption (rather exclusion) levels for radionuclides of natural origin as shown in Table 1 of the SG. 3. My main observations are as follows: (a) According to Computer Codes developed separately (about ten years ago) by my group and by colleagues from the Soreq research center, it turns out that this equation can lead to "acceptable" annual doses from building materials in the range of 3-5 mSv/y and in certain cases - even greater than 5 mSv/y. (b) Regarding IAEA's distinction between "10 up to few tens of a mSv" for normal (routine) uses and "up to 1 mSv" for accidental events - as basis for exemption levels (mainly for artificial, amenable to control, radionuclides) - it should be emphasized that if this equation is generally adopted, the doses incurred by residents from building materials during normal use of houses, could be significantly higher than "exemption dose criteria for rare accidental events". (c) The doses, as it appears in the proposed equation, do not include exposures from radon, which are mentioned as a possible incentive for the competent authorities to apply stricter values for Ra226 activity concentrations. (d) In my opinion, and according to our approach in Israel, the exposures from building materials can be considered "amenable to control", and can practically be controlled e.g. by (1) authorizing uses of the vast majority of domestic raw materials; (2) limiting the import of highly radioactive raw materials from abroad; (3) limiting the marketing of both domestic and imported building materials which do not comply with specific dose criteria. (e) Moreover, considering the above mentioned actual worldwide (including European) "representative" annual exposures from building materials, it seems highly unjustified to set activity concentration criteria, leading to exposures greater than typical exposures by an order of magnitude and even more. (f) Of course, I am aware of potential retrofitting difficulties that may arise, especially in extreme cases, if the criteria are set apriori to exclude those extremities; but on the other hand, please consider, as an example, the situation in our country which, I believe is very common. The average exposures from building materials are in the range of 0.3-0.5 mSv/y with extreme values up to 1-1.2 mSv/y. Applying the proposed equation, would mean that those relatively highly radioactive building materials (such as bricks, ceramic tiles etc.) causing, say, 3 mSv/y could be freely, rather unlimitedly manufactured and/or imported. (g) The problem becomes even more severe, if important characteristics of building materials are considered. Everybody has to live somewhere, which means that additional individual doses ("encouraged" by relatively lenient dose criteria) may end up in additional, rather significant, collective doses. Additional 0.2 mSv/y caused by a particular building material, may lead to several hundreds up to several thousands man-Sievert per year. And this may apply even if a small fraction of the population is practically exposed to the new product. By the way, in the example shown in (f), if only 500,000 people out of a population of 7 million were exposed to the new material, an additional collective dose greater than 100 man-Sievert could have been caused. (h) Public opinion usually tends to regard radioactive materials of natural origin as "more acceptable" than materials containing artificial radionuclides, mainly as far as "old" (compared to "new") risks are considered. Nevertheless, it is my serious concern that possible situations, in which "green" groups will start counting "additional cancer fatalities" caused by "almost unlimited uses of building materials", cannot be ruled out. This could happen, if such groups were smart enough to mention and/or to utilize e.g. the controversial findings of BEIR-7, claiming inter alia that LNT is a reality rather than a hypothesis and that low level doses do have the potential for causing cancer as well as other diseases. (i) Finally, although the origin of radionuclides in building materials is natural, I am not sure that this is the only way the public is considering it. The fact that radionuclide concentrations in building materials can be easily modified (e.g by dilution, or by controlling coal ash additives and other mixtures, or even by applying "anti – radon paints" to reduce radon exhalation), may divert, at least to a certain extent, public attitudes toward exposures from building materials. Also, the fact that building materials are basically industrial products, not "pure soil"/"pure rock" can play an important role in this direction. 4. I do hope that these observations will be considered by the distinguished members of the Task Group, all of whom I happen to know personally.