What is the environment, and in particular the environment that can have an impact on our health? What is its nature? How do we conceptualise it? The environment, in the broadest sense of the term, is at the heart of some of society's most pressing challenges. It raises issues that can only be tackled by combining scientific research with the views of the general public. There is a growing awareness among the latter, not only of the impact that the environment, as we have transformed it, can have on our health, but also of the way in which our habits and experiences throughout our lives are changing us and may contribute to the development of certain diseases. The EnviroParCiPhil project raises the question of participatory research methodologies that could be used on a large scale to change the definition of the (spatio-temporal) boundaries of the environment as a determinant of our states of health and disease. The aim is to establish collaboration between scientists and citizens in order to co-develop a methodology that can be replicated on a large scale to gain a better understanding of 'health-environment' issues. The aim is to listen to the views and questions of members of civil society in order to broaden the scope of research in the biomedical sciences and the humanities and social sciences into the environmental determinants of disease, and thus to strengthen the relevance of this research from a purely epistemic point of view but also at the service of citizens directly concerned by "exposures" and the public health policies that can protect them from these exposures. The object of the co-construction is therefore to co-develop a method for amending the concept of environment in health within the framework of cohorts, and to enable cohort members to become more involved in developing future research questions and analysis methodologies that will concern other epidemiology projects. This methodology therefore has an iterative dimension, with the concepts of environments expressed also being studied in philosophy of science on subsequent cohorts. The aim of this pilot project is to set a precedent and encourage researchers to use, in health-environment studies, research methodologies that mobilise participation as a conceptually and pragmatically enriching tool in interdisciplinary research, for example with the co-design of intervention studies. At the end of the project, a colloquium will bring together researchers from the fields concerned to assess the results of the project and to study the feasibility of using the methodologies generated in future research.