Precaution is today referred to as a concept and a tool for the regulation of food and environmental risks. Although the definitions for precaution vary, they always raise the question of uncertainty in the assessment of the risks. Literature in environmental, legal and social sciences have mostly focus on the regulatory side of precaution, often considering precaution as a dispensation of risk assessment. However, as showed by the multiplication of guidelines on the communication of uncertainties in risk assessment, as well as proposals aiming at improving the adequacy of risk assessment for decision making under uncertainty, a important aspect of precaution relates to the scientific assessment of risks.

The issue of precaution in risk assessment has seldom been analyzed. When it has been approached, it has been either in a prescriptive way or as a component secondary to the analysis of risk assessment policies, participation of profanes or scientific expertise.
This interdisciplinary thesis seeks to understand how precaution enters food risk assessment and how it produces different methodological and analytical choicies according to the status of the risk assessment (agency, university, non-governmental organisation), the risk assessment procedures, the regulatory framework and the degree of public controversy.

The thesis focuses on two case comparative case studies of risk assessments carried out in Europe and in the US : perchlorate and bisphenol A. In addition, the results of the case studies are weighed against the analysis of the expression of uncertainties, the reference to precaution and the principle results of the food contaminant risk assessment and risk management document stored in the Holyrisk database (see HolyRisk). The outcome of the thesis is to provide a framework for precaution in risk assessment based on existing practices and the actual use of scientific information in regulatory decisions.