Potential Contamination Cases in Anti-Doping: Experiences and Practices of 33 Anti-Doping Organisations

Unintentional doping, the inadvertent ingestion of or exposure to substances on the World Anti-Doping Agency's Prohibited List, is an increasing concern in sport, with potential sources ranging from dietary supplements and contaminated foods to pharmaceuticals, intimate contact, and the wider environment. When an adverse analytical finding (AAF) is reported, Anti-Doping Organisations (ADOs) must distinguish doping from inadvertent exposure, a task that carries real consequences for athletes' careers. Yet little is known about how ADOs handle such cases in practice. Through the Monitoring Group of the Council of Europe's Anti-Doping Convention, we conducted an electronic survey of National Anti-Doping Organisations and International Federations on their experiences and practices for managing potential contamination cases during 2024-2025. Thirty-three ADOs, predominantly from Europe, responded. The majority (85%) had encountered at least one contamination case during the period, yet only 36% had a standardised process for handling such cases. Athletes claiming contamination, however, were rarely successful in defending their case. ADOs reported 46 unique prohibited substances and 71 source-substance associations being involved in alleged contamination cases, with dietary supplements the most frequent source (76%), followed by food (42%). Adoption of standardised processes increased with the operational scale of the ADO, leaving smaller organisations least equipped. These findings show that potential contamination cases are now a routine reality for ADOs, but the procedural tools to manage them are not. The evidence collected here will inform forthcoming Council of Europe's best-practice recommendations aimed at protecting athletes while preserving the integrity of clean sport.