The problem is the concept of absorbed dose in its various forms. Clearly it cannot be employed safely for internal irradiation particularly from particles or element which concentrate e.g. on DNA. There is also a problem with dose averaguing over time. The problem has been reviewed in ECRR2003 and in the CERRIE minority Report and conceded in the CERRIE Majority Report Section 11. Therefore any comparison with external irradiation and internal is unsafe and we are thrust back on top epidemiology for illumination. Whilst epidemiology shows us that ICRP models are out by a factor of about 300-fold for general internal exposure to fission products the factor of error is unequivocally shown by the various studies of infant leukemia after Chernobyl in the in utero cohort. ECRR has begun a reassessment of internal risks through development of new weighting factors. However, since it is ionisation density at the target that is of interest, in principle, this can be calculated for various defined exposures. The risk model that ICRP continue to use is an application of scientific method since it uses deduction based on external risk experiments to inform internal exposure risks. Cheers Christo