Control of low-level radiation exposure: what is the problem and how can it be solved?

The carcinogenic risks of exposure to low-level ionizing radiation used by ICRP have been challenged as being, at the same time, both too high and too low. This paper explains that the epidemiological evidence will always be limited at low doses, so that understanding the cellular mechanisms of carcinogenesis is increasingly important to assess the biological risks. An analysis is then given of the reasons why the challenges to ICRP, especially about the linear nonthreshold response model, have arisen. As a result of considering the issues, the Main Commission of ICRP is now consulting on a revised, simpler approach based on an individual oriented philosophy. This represents a potential shift by the Commission from the past emphasis on societal-oriented criteria. These proposals have been promulgated through IRPA, and an open literature publication was published in the Journal of Radiological Protection in June 1999. On the basis of comments received and the observations presented at the IRPA 10 Conference, the Commission will begin to develop the outline of the next recommendations. It is now more than 10 y since ICRP distributed, for comment, a draft of what was to become the publication of the 1990 recommendations. The Commission plans to develop its new recommendations on a time scale of the next 4 or 5 y. In this paper, many of the issues that will need to be addressed in the development of the recommendations will be identified. These issues will cover biological effects, dosimetric quantities, and the establishment of those levels of dose at which different protection requirements will be put into place. Concepts of exclusion and exemption will need to be clarified as well as the meaning of how to achieve what the proposal identifies as "as low as reasonably practicable." Finally, the Commission has decided to develop an environmental radiation protection philosophy that will need to be developed as part of the new recommendations.