Panel discussion: Do non-targeted effects impact the relation between microdosimetry and risk?

An invited panel discussed with the participants of the Symposium their views on the impact of non-targeted effects on the relationship between microdosimetry and risk. The discussion was wide ranging and lively, with divergences of opinion. At one end was the view that understanding microscopic features and distributions of radiation was an essential component to understanding risk, especially at low doses, and additionally that substantial questions and uncertainties arose from lack of information on the mechanisms and consequences of non-targeted effects. At the other end, it was held that microdosimetry and non-targeted effects are irrelevant to practical radiation protection because protection practice is already securely founded on macroscopic organ doses and direct epidemiological observations of risk. A summary of the discussion is provided in the sequence in which it took place. The session illustrated the underlying mixture of fundamental and practical issues and the need for increased scientific knowledge.