The history and perspective on quality factors proposed by the International Commission on Radiological Protection...

Proper consideration of the relative biological effectiveness (RBE) is essential for evaluating potential health risks associated with exposure to cosmic radiations spanning a broad range of linear energy transfer (LET). The quality factor as a function of LET, Q(L), empirically proposed and refined by the International Commission on Radiological Protection (ICRP), remains central to assessments of relatively low-dose cosmic radiation exposures, despite the primary use of radiation weighting factors (w_R) in terrestrial protection frameworks. This article reviews the historical development of the Q(L) function and examines the adequacy of its application to cancer risk analysis. To this end, we first confirm its numerical consistency with a more sophisticated quality factor algorithm adopted by NASA through a comprehensive literature review. We then evaluate the appropriateness of the maximum value of Q(L), using a meta-analysis of RBE data for mouse tumor induction by fission neutrons. Finally, we discuss future perspectives on Q(L), emphasizing its strong relevance to measurements not only in space dosimetry but also in medical physics.