Our research is based on an interdisciplinary collaboration between CETESB (Environmental Agency of the State of São Paulo), and two research teams, Territoire (UMR PACTE n°5194) and Cresson (UMR AAU n°1563), from France. It aims to test various qualitative methods to implement participative risk communication among the populations of at-risk areas in the São Paulo Metropolitan Region. We are particularly interested in the Barão de Mauá residential complex, located in the city of Mauá, 30 km from São Paulo, which is a life-size laboratory to study a risk situation involving soil and groundwater contamination. In this context, our contribution is to implement two very complementary approaches: an approach via the controversies, which brings the positions and thinking of the various actors involved in this risk situation up to date, and an approach that describes the ambience of the condominium in a way that reflects as closely as possible the inhabitants' lived experiences. The analysis of controversies can be used as a methodological tool to analyze the actors who are mobilized, the arguments that are made, the objects that circulate and are transformed and the agreements that emerge and dissolve in order to identify the salient aspects and analyze the bottlenecks. Regarding the approach within the ambiance, there was an anthropological immersion of a French-Brazilian research team in the Barão de Mauá condominium over a period of five days. An original inquiry was implemented to develop a substantial sensory ethnography of this contaminated environment. The hypothesis that guided this work is that a risk atmosphere is embodied and manifested in sensory perceptions, physical and memorial traces, daily gestures, ordinary narration, emotional tones, specific landscapes and ways of being together. Both approaches proved very complementary to various points of view: in the implementation of various time scales involved in the situation of risk (long temporality 1 This work is part of a dual research framework: a CNRS PEPS Interdisciplinary FaiDoRA programme, "Low Doses, Risks, Alerts" (AAU-CRESSON, France), and a FAPESP when it falls under the socio-political history of the area and short when it relates to the inhabitants' day-today experiences), in the articulation of the various levels of analysis involved (actors logical analysis and experiment inhabitants). The combination of these two approaches broadens the concept of risk communication by giving all due importance to the qualitative perception of risk and the complexity of vulnerable situations and leading to a proposal for participatory risk communication.