Because risk can not be perceived directly, risk communication becomes highly significant. Studies on risk perception show that experts and lay persons differ in their concepts of risk. Experts use a two dimensional concept: probability times severity of harm, lay persons have a multi-dimensional concept of risks taking characteristics of consequences and situations into account (Fischhoff et al., 1981; Jungermann, 1991; Wiedemann, 1992). The accelerating development of technologies and their inherent risks and hazards leads to an increasing importance of adequate communication. Over the last thirty years changes in the way of communicating risk can be observed.