The societal decision to manage a particular risk is a complex process that is anchored in prioritization. By prioritization we mean the ordering of risks in terms of their size (i.e., probability of occurrence and health or environmental consequences), public perception, controllability, and socioeconomic and political impact. Prioritization reflects society’s valuation of risks. Prioritization does not correlate completely with risk magnitude or severity. Resources are limited to manage risks, and society’s decisions regarding priority provides some rationale for how resources should be allocated.