''How small is small enough?'' or the limits of optimization

In order to kick-off a discussion of the reasons underlying the limits and reference values in radiation protection, the different types of exposures and exposure situations are discussed under these aspects. Arising problems are identified and a proposal for a trivial (de minimis) annual dose of 0,1 mSv is made. The outstanding importance of educating and preparing society for the process of optimization in existing and emergency exposure situations is emphasized.