Cooperation between higher education and the police has been described an often conflict-related “two-worldthinking”. This study draws on interviews with 16 PhD-educated police officers and explores what kinds of academic credentials they experience that the police regard as dangerous, and how the police organisation responds to such danger. By combining the concept of symbolic closure with the theory of purity, danger and pollution, the study explains how the organisation seeks to neutralise both the credentials and their carriers. Dangerous pollution are perceived in three different themes. First, the research carried out by the PhD-educated police officers is perceived as inaccessible in both contentand form, prompting disinterest and alienation of its carriers. Second, it is perceived as irrelevant to the profession and thus ignored. Third, it is perceived as critical of the organisation, leading to questioning and exclusion of its carriers.