ICRP 2005 Recommendations The ICRP establishes the 2005 Recommendations as an evolutionary step from previous recommendations, rather than a revolutionary step. As a practicing health physicist, I agree with the ICRP’s prudent approach. The spectrum of opinions, both professional and lay, spans an incredibly diverse range of genuine and hypothetical biological effects. Some people feel a personal terror regarding anything radioactive that, in most instances, far exceeds any possible or real effect. Many people believe there is ample evidence that biological effects at low doses include a threshold or even hormesis. The 2005 Recommendations, I my opinion, miss a choice opportunity to elaborate on the various paradigms that can be used to model biological effects at doses less than 10 or 20 rem. I think a succinct presentation of the low-dose models along with studies that support or refute the model would be enlightening. An erudite discourse on the information available, much of which has been available for decades, would be the true evolutionary step. Except in a few select cases, the ICRP chooses to continue promoting the linear nonthreshold (LNT) model for estimating biological effects at low doses. I have no problem with the use of the LNT model, but I, and many others, have serious concerns with its abuse. A forthright description of the biological models that may represent low dose effects can lead to the administrative decision to retain the LNT for precautionary reasons. I present the low-dose models, including the supralinear model and hormesis, in my basis training course and summarize that the LNT model presents a conservative estimate of risk, hence insuring worker safety. Students find the discussion informative and sincere, and as such, places the focus on “promoting safety” as opposed to “controlling risk”. Specific Changes: Para 101. “it is scientifically reasonable”. Recommended change: “it is administratively reasonable”. Reason: Earlier in the paragraph the ICRP recognizes exceptions and “judges the weight of evidence” hence science has very little to do with the ICRP’s recommendation. Para 102, “In arriving at this practical judgment” Recommended change: “In arriving at this convenient judgment”. Same reason as above. Para 102, This paragraph flippantly waves off the vast amount of data relating to low dose biological effects, especially those effects that do not support LNT. Considering the huge store of data and research, I regard the content as evading a meaning dialogue. This is where a discussion of relevant models of biological effects should be inserted. Para 158. “The worldwide average annual effective dose form all natural sources, excluding radon, quoted in the UNSCEAR (2000) report is 1.2 mSv with a range of 0.8 mSv to 2.4 mSv.” The upper natural dose limit of 2.4 is misleading. How can UNSCEAR and the ICRP use this value when there are people living in parts of the world that are exposed to appreciably higher doses. Such places include: Ramsar, Iran; Guarapari, Brazil; and Kerala, India. The range should include the natural dose to the highest exposed indigenous people. Para 133. Dose constraint From an implementation point of view, a dose constraint is essentially the same as a limit.