BIOLOGICAL EFFECTIVENESS OF LOWER-ENERGY PHOTONS FOR CANCER RISK

For risk assessment of photon exposures, the energy-dependence of relative effectiveness may be required. The NCRP has recently addressed this need by reviewing the available evidence from various fields of study and making recommendations for the effectiveness ratio of lower-energy photons, for the purposes of quantitative uncertainty analysis for specific cancer risk assessments where lower-energy photons and electrons are involved. The present paper provides a personal discussion of selected aspects of the evidence and analysis; it highlights the key role of low-energy electrons in determining biological effectiveness.