Health risks attributable to radiation

Draft document: Health risks attributable to radiation
Submitted by E Janet Tawn, Westlakes Research Institute
Commenting as an individual

I appreciate the opportunity to review the Foundation Document FD-C-1. My comments concern Section 6 Risks of Heritable Disease. This is a particularly complex area. I was therefore surprised to see so much overlap between the text in UNSCEAR 2001 and the text in this document, with some sections a direct copy of what has been presented by UNSCEAR. Whilst I accept that ICRP make use of UNSCEAR deliberations it would be helpful to have a new perspective on the UNSCEAR work and an interpretation that could more readily be understood by the non-specialist. Data from Table 6.6 is apparently the basis for the statement on page 45, lines 1698-1703 that heritable risk for the whole population is around 20 cases per 10,000 people/Sv. A comparison is made with the previous ICRP risk estimate of 100 cases per 10,000/Sv. However, this is not a valid comparison since Table 6.6 risk coefficients are based on continuous exposure and assume that every generation carries its own risk plus a heightenened risk inherited from the previous generation. Thus the estimate is a two generation risk whereas the previous estimate in ICRP 60 was for all generations. Furthermore it needs to be made clear, when quoting Table 6.6 on page 45 that the risk is for any given population receiving continuous exposure generation after generation. Nominal risk for a working population is given in Table 4.1b, line 1998, as 12. I assume this is derived using the same methodology as in ICRP60 but no information on this is provided. UNSCEAR derive risks for progeny of those exposed whereas the ICRP approach is to apportion the risk directly to the exposed population.Thus first generation risks are currently derived for the total exposed working population based on the assumption that the genetically significant dose will only be applicable to those of reproductive age. On this basis, overall risks are derived for a working population which are lower than those for a reproductive population. This approach enables heritable risks to be accommodated in the overall structure of risks and detriment. As such, it may be appropriate for radiological protection practices applicable to the working population as a whole, but it ignores the fact that the genetic risk is not the same for all workers. Those of reproductive age are actually a subset at greater risk whereas those who are past reproductive age are at no risk. If, as is proposed, a two generational risk model is to be used to evaluate risks for occupational exposure, there needs to be a better explanation of how the risk is made up of two components i.e. a direct first generation risk to the offspring of the exposed workers plus an additional risk to the second generation of any adverse outcomes in the offspring being passed to the workers’ grandchildren. Whilst I can follow the logic of calculating the first generation risk for a total working population based on assumptions regarding the reproductive proportion, it is not clear to me that the second generation risk can be calculated in the same way, and it would help to have further explanation of the reasoning behind this. The current approach provides no guidance for physicians who may need to provide information to individuals or specific groups of workers about heritable risks. Men of reproductive age need to know their risk of having a child with a genetic disorder and radiological protection practices should acknowledge this. Furthermore, a theoretical risk of having a grandchild with a radiation-induced genetic disease becomes, in practice, irrelevant if the first generation offspring are apparently normal. In conclusion, I would prefer to see an independant description and assessment of the work undertaken by UNSCEAR on the methodology of deriving genetic risks, and a more detailed description in section 4 of how these risks are incorporated into the radiological protection strategy. Furthermore, if genetic risks are to be averaged over the whole working population for radiological protection purposes then further guidance needs to be provided for counselling workers of reproductive age.