The risk linked to ionizing radiation: An alternative epidemiologic approach

Radioprotection norms have been based on risk models that have evolved over time. These models show relationships between exposure and observed effect s. There is a high level of uncertainty regarding lower doses. Recommendati ons have been based on the conservative hypothesis of a linear relationship without threshold value. This relationship is still debated, and the diver se observations do not allow any definitive conclusion. Available data are contradictory, and various interpretations can be made. Here we review an a lternative approach for defining causation and reconciling apparently contr adictory conclusions. This alternative epidemiologic approach is based on c ausal groups: Each component of a causal group is necessary but not suffici ent for causality. Many groups may be involved in causality. Thus, ionizing radiation may be a component of one or several causal groups. This formali zation reconciles heterogeneous observations but implies searching for the interactions between components, mostly between critical components of a ca usal profile, and, for instance, the reasons why specific human groups woul d not show any effect despite exposure, when an effect would be expected. r adiation protection, radiation risks, risk factors.