The CIREs are often consulted by the DDASS when organizations request epidemiological studies or health monitoring around specific sites—whether currently polluted or potentially at risk of pollution—with the aim of determining whether the site is causing health effects among nearby residents. In these situations, the CIREs are often called upon to outline the advantages and limitations of the various possible approaches to providing answers. Epidemiology or health surveillance are rarely the most appropriate tools, but dialogue with stakeholders is absolutely necessary for such an analysis to be shared. Characterizing contamination in exposure environments is often an essential first step and requires the collaboration of numerous stakeholders. Two cases currently being addressed by the Rhône-Alpes Cire are presented here as examples. (R.A.)