Sensible Advice for Making More Realistic Assessments of Dose for Biota Under Different Exposure Situations.

One of the first issues to arise in the development of a set of Reference Animals and Plants by the International Commission on Radiological Protection (ICRP) was that of allowing for factors such as relative biological effectiveness (RBE) in considerations of estimates of dose (ICRP, 2003, 2008). The issue was not a new one. The need to consider such factors had been widely recognised for many years, and for several reasons. Firstly, RBE obviously applies to animals other than humans; indeed, much of the RBE information used in human radiological protection had been derived from both in-vivo and in-vitro animal studies. It thus seemed reasonable that allowance should be made for such information in assessments of the relationship between dose and effects for those same animals in the context of their exposures to radiation in an environmental context. Secondly, it was known that many animals and plants can accumulate concentrations of naturally occurring alpha-particle-emitting nuclides within their tissues to very high levels, and thus there had been arguments for the use of ‘weighting factors’ to normalise assessments of comparative radiation background dose rates amongst different types of fauna and flora. Finally, because of the presence of alpha-particle-emitting nuclides (and, in some cases, tritium) in many environmental areas, as a result of different exposure situations, there had been concerns that their potential effects on wildlife would be underestimated if allowances for RBE were not taken into account.