Risk assessment is now firmly enshrined in environmental protection policy. It is often thought of by policy-makers as an apolitical activity, driven by ‘neutral’ technical experts, producing ‘objective’ results based on clear and firm scientific foundations. As a result, risk assessment possesses a privileged voice in the decision-making processes relating to the amelioration of environmental hazards. The paper suggests that this view is simplistic and uncritical. Complex contextual factors such as personal/organizational values and interests contribute to definitions of and responses to risk. From this starting point, we analyse how risk assessment is structured by its politico-social context; how its outcomes may be contested and marginalized in deliberations over the remediation of potentially hazardous sites; and how the lay public may be excluded from the process. These arguments are illustrated and discussed through a detailed case study of deliberations over the threat posed by a highly contaminated site in an urban setting in England. Recommendations are made for improving public trust in and engagement with current policy and practice.