What role for social scientists in risk expertise?

When it comes to risks -- health and environmental risks, like those linked to the use of nanotechnologies, pesticides, etc. -- three main groups of actors are easily identified, brought together through boundary organisations such as environmental and sanitary risk agencies: the natural and technical scientists, who provide their expertise to assess risks (especially toxicologists, epidemiologists and microbiologists); the policy makers, who take decisions regarding risk management and risk regulation; the lay public, who are more and more involved in participatory frameworks. Sometimes three other groups of actors are added: the 'economists' who can for instance conduct cost--benefit assessments or multi-criteria analyses (especially ecological economists, public economists, political economists and social economists); the 'philosophers'/'ethicists' who can use ethics to highlight moral choices and responsibilities in face of risks; and the 'jurists'/'legal experts' who can justify authorisation or interdiction according to law. Inversely, there is a group of actors which is not clearly identified, that of social scientists, even though a considerable quantity of social science knowledge on risk has been produced. Why is there such a discrepancy? This article, based on a critical review of the literature, aims to make sense of the fuzziness surrounding the involvement of social scientists when it comes to risk expertise. The article shows that one reason for this puzzling situation is to be found in the gap between what social scientists often want to do when they are called in as risk experts and what natural scientists and public policy makers actually expect from them.