CBRNe in Mass Gatherings: A Comprehensive Narrative Review of Threats and Vulnerabilities

Abstract

Context: Mass gatherings can place substantial demands on health systems and emergency response capacities and may create unique vulnerabilities to chemical, biological, radiological, nuclear, and explosive (CBRNe) incidents. Despite growing attention to mass gathering preparedness, evidence specifically addressing the spectrum of CBRNe threats and vulnerability pathways across different types of mass gatherings remains limited. This review aimed to identify the major CBRNe threats associated with mass gatherings and to characterize the key vulnerability pathways and contextual factors that may influence their occurrence and consequences. Evidence Acquisition: A narrative review was conducted using PubMed and Scopus, supplemented by official sources from organizations including the World Health Organization and the Centers for Disease Control and Prevention. Searches combined CBRNe-related terms with those related to mass gatherings. English-language articles, official guidelines and reports, historical case reports, and relevant textbooks published or prioritized between 2000 and 2026 were included. Findings were synthesized narratively and thematically according to mass-gathering characteristics, CBRNe entry pathways, and threat domains. Results: The review identified common vulnerabilities across mass gatherings, including high population density, prolonged event duration, restricted evacuation routes, diverse and mobile populations, variable security, adverse environmental conditions, and limited emergency resources. CBRNe agents may enter mass gatherings through deliberate or accidental release, secondary contamination, or environmental sources. Chemical and explosive threats appeared particularly plausible, whereas radiological and nuclear incidents, although less frequent, may have substantial psychosocial and operational consequences. Religious, sporting, political, and cultural events; spontaneous gatherings; refugee and displaced-person camps; and transportation hubs demonstrated distinct yet overlapping vulnerability profiles. Conclusions: CBRNe preparedness should be integrated into routine mass gathering planning through hazard-based risk assessment, surveillance, detection and decontamination capabilities, medical surge preparedness, responder training, interagency coordination, and risk communication.