Introduction
Mass gatherings, as a social and urban phenomenon, have become one of the major challenges in urban management in recent decades due to population growth, the expansion of cultural and religious events, and increased social interactions (World Health Organization, 2008). These events, which include religious, sporting, political, and cultural gatherings, put significant pressure on urban infrastructure, service resources, and the health system by gathering large numbers of people in a specific time and place (Milsten et al., 2002). While managing mass gatherings requires a multidimensional and coordinated approach, previous studies have primarily focused on macro-level aspects, such as population dynamics, collective behaviors, and crowd modeling (Helbing et al., 2007). In contrast, micro-level aspects and operational issues such as electrical safety, food hygiene, and waste management have received less attention, even though these factors play a decisive role in maintaining the health and safety of participants (Thompson, 2008). The lack of structured frameworks for continuous monitoring and evaluation of health, safety, and environmental (HSE) performance in mass gatherings is considered a serious gap in the research literature. Many existing models lack operational capability in real-world situations and are unable to effectively identify and manage micro-risks and hidden threats (Safipour et al., 2023). Additionally, existing assessment tools are often designed in a non-comprehensive manner, unable to simultaneously cover the three dimensions of health, safety, and environment (AlMarri et al., 2025). 
Given the complexity and diversity of threats in mass gatherings, there is a strong need to design a comprehensive and practical tool for evaluating HSE performance in an urban context; a tool that can monitor HSE indicators in a structured manner and help executive managers make quick and effective decisions. The present study, using expert opinions, field data, and practical experiences, aimed to design and validate a tool for evaluating HSE performance in mass gatherings that covers the three main dimensions of health, safety, and environment in an integrated manner. This tool can be used as a practical guide for city managers, event organizers, and responsible institutions in crisis management.

Literature review
The World Health Organization (2008) defines mass gatherings as “an organized or unplanned event where the number of people attending is sufficient to strain the planning and response resources of the community, state, or nation hosting the event”. Milsten et al. (2002) have reviewed medical experiences in major mass gathering events, emphasizing the need for health system preparedness and emergency response protocols. Thompson (2008) highlighted the critical role of public health planning and coordination for mass gatherings among organizations in reducing health risks. 
Among studies related to the health domain, Hutton et al. (2024) examined the perspectives of managers, law enforcers, and medical staff involved in organizing mass gathering events and found that the lack of effective communication between these groups can lead to disruptions in the health and safety management of events. In another study, Hutton et al. used focus group discussions to highlight the differences in the understanding and practices of risk management by each group and emphasized the need to design common and understandable tools for all stakeholders involved in organizing mass gatherings (Hutton et al., 2025). Bahbouh et al. (2024) also presented a framework for health management in mass gatherings, which includes algorithms for population monitoring, early warning, and emergency response planning. These frameworks offer predictive capabilities and rapid response by leveraging new technologies, including image processing and social network data analysis. 
Among studies related to the safety domain, Helbing et al. (2007) modeled collective behavior in panic situations and demonstrated that the absence of emergency exit routes, inadequate urban space design, and unpredictable population reactions can lead to humanitarian disasters. Safipour et al. (2023) designed a resilience model for religious gatherings, using indicators such as crisis severity, probability of occurrence, and response capability in risk assessment, which can be used in the safety management of urban events.
Among studies related to the environment domain, Johansson et al. (2012) showed a link between population density, increased pollution, and the prevalence of respiratory diseases in urban settings. Also, the Centers for Disease Control (CDC) guidelines emphasize the importance of controlling environmental factors such as ventilation, ambient temperature, and water quality in mass gatherings. Johansson et al. (2012) indicated the weakness in waste management and the lack of sustainable infrastructure in urban events, which can lead to pollution of natural resources and a threat to public health.
Among studies related to HSE performance, Sadoughi et al. (2012) employed a fuzzy analytic hierarchy process (AHP) model to develop a performance evaluation model for HSE management systems, which includes both enabling and outcome-based indicators. This model can be applied in industrial settings but requires adaptation to the specific conditions of mass gatherings. Tools such as HSE-P10 and specialized HSE dashboards have also been developed to monitor HSE performance in large projects (AlMarri et al., 2024).
Despite these studies, the lack of a comprehensive, structured, and operational tool for evaluating HSE performance in mass gatherings, especially in urban settings, remains a serious research gap. Most of the existing models either partially address one of the HSE dimensions or are designed for industrial and non-urban environments and are not capable of adapting to the real conditions of urban events. Aiming to fill this gap, the present study seeks to design an HSE evaluation checklist for mass gatherings that covers the three main dimensions of health, safety, and environment in an integrated and practical manner.

Materials and Methods
This is a descriptive-analytical study conducted in Tehran, Iran. The process of designing and testing an HSE performance evaluation checklist was carried out in six stages. 

Primary data collection
In the first stage, basic data for compiling checklist items were collected through field visits, risk assessment, analysis of past events, and review of non-compliance reports. The research team visited the religious and cultural gatherings, observed the environmental and operational conditions, and documented potential hazards. These hazards included non-standard wiring, lack of fire extinguishing equipment, poor food quality, improper waste disposal, and noise pollution. The identified risks were categorized and prioritized using a probability-severity matrix to form the basis for designing the tool items. The matrix used for risk assessment at this stage is shown in Table 1. The history of previous incidents during mass gathering events in urban settings was reviewed to identify patterns and factors that contribute to the occurrence of incidents. During mass gatherings, minor incidents may occur, including people slipping, electrocution, falling scaffolding, and people falling from elevated surfaces such as performance stages, etc., which are analyzed for the 22 districts of Tehran. Only recorded incidents that were officially sent to the Tehran Municipality HSE Secretariat were analyzed. Data from HSE inspections of previous mass gatherings held in Tehran Municipality (Imam Reza Celebration, Ghadir Celebration, Arbaeen Remnants Walk) were analyzed to identify deficiencies in the management of mass gatherings.

Refining items
Based on the collected data, an initial list of items related to the three main axes of health, safety, and environment in mass gatherings was prepared. To refine and complete this list, group meetings were held with the participation of 10 HSE experts. This panel of experts was purposefully selected from three groups of specialists (Table 2) to consider different executive, technical, and scientific perspectives in refining the items.

Preparation of the checklist
The final items were organized into three dimensions of health, safety, and environment and designed as an operational tool. For each item, the legal requirements and related upstream documents were included in a separate column, allowing users to cite and implement. This checklist was tailored to the specific conditions of Tehran and the needs of urban management.

Validation of the checklist
To determine the face validity of the checklist, the initial draft was presented to 10 experts. The items were reviewed for clarity, comprehensibility, and importance. At this stage, 5 items were revised, and two items were deleted. 
To determine content validity, each expert rated the necessity of the items at three levels, and the content validity ratio (CVR) for each item was calculated using the Lawshe method. Items with a CVR ≥0.62 are acceptable. It was found that 92% of the items had acceptable CVR. Seven items with lower CVRs were modified or removed. Experts also rated each item on a 4-point scale for relevance, clarity, and simplicity, and the content validity index (CVI) for items and subscales was calculated. The CVI for all items ranged from 0.80 to 1. The CVI average for the entire checklist was calculated to be 0.92, indicating an excellent content validity.
To assess reliability, the final checklist was administered to 50 people in three urban gatherings. Cronbach’s α coefficient was calculated to be 0.86 for the entire checklist. Regarding its subscales, Cronbach’s α value was 0.83 for safety, 0.80 for health, and 0.78 for environment. All values ​​are above the acceptable threshold (0.70) and indicate favorable internal consistency and adequate reliability of the checklist and its three subscales.

Results
In Table 3, the concepts and components extracted for developing the checklist are presented for three domains of safety, health, and environment. For each concept, the relevant national legal requirements and upstream documents are also listed. Using leading and lagging indicators, items were first formulated and the AHP method was used to determine the relative importance (weight) of each question, rated as 1 (Full compliance with the regulations), 0.5 (Partial or incomplete compliance), or 0 (No compliance). The score for each item is calculated as: Weight%  × Compliance level. Then, the scores of all items in each domain are summed and normalized to a scale of 0 to 100. The final HSE score is obtained by weighting the three domains of safety, health, and environment. The total score of the checklist is obtained by summing the total scores of three domains. The final version of the checklist is provided in the  Appendix 1.

Discussion
The results of using the checklist for HSE performance evaluation in mass gatherings in urban areas showed that many operational components in the field of HSE have been neglected in current planning. These findings are consistent with the previous studies that have shown existing shortcomings. Studies such as those by Sadoughi et al. (2012) and Bahbouh et al. (2025) in Iran primarily focused on macro-level assessments in industrial settings or national crises. Some national studies have only addressed qualitative assessments of participant satisfaction or descriptive analyses (e.g. Johansson et al., 2012). Low attention has been paid to operational components in the urban context. The checklist designed in our study, using field visits, risk assessment data, and expert opinions, was able to identify and structurize micro- and operational indicators at the local level, particularly in the areas of electrical safety, temporary structures, food hygiene, and waste management. The checklist had high validity and reliability. High Cronbach’s α coefficients for all three dimensions of the checklist indicated the high internal consistency of the checklist. Overall, the checklist was able to reduce the gap between theory and practice in HSE of mass gatherings in urban areas, paving the way for improving the quality of HSE management in urban events. This tool can not only be used in the event planning phase, but can also be utilized as an implementation framework in the performance monitoring and auditing phases (Appendix 1).

Conclusion
By focusing on micro and operational components, including electrical safety, temporary structures, food hygiene, waste management, and legal requirements, the designed checklist can identify and address gaps in current planning for mass gatherings in urban areas in Iran. The checklist has high content validity and reliability (internal consistency). The following recommendations are provided:
Utilizing the designed checklist in the initial planning phase of mass gatherings by municipalities, crisis management organizations, and executive bodies
Training contractors and executive staff based on the items of the designed checklist, particularly in the areas of structural safety, environmental health, and waste management;
Development of digital systems for real-time monitoring of HSE indicators in mass gatherings and connecting them to management dashboards;
Utilizing the designed checklist in the audit and performance evaluation process after mass gatherings for continuous improvement.
Future studies are recommended to: 
Use the checklist in various cultural, religious, sporting, and commercial mass gatherings; 
Conduct a comparative analysis of HSE performance using the checklist in different cities of Iran, which have different infrastructures and climatic conditions; 
Develop smart versions of the checklist with the ability to connect to environmental systems, urban sensors, and early warning systems; 
Assess the level of acceptance of /satisfaction with the checklist among users and explore the implementation barriers.

Ethical Considerations

Compliance with ethical guidelines
This study did not involve human participants or identifiable personal data; therefore, no institutional ethical approval was required. Nevertheless, the authors adhered to all ethical guidelines for scholarly research, including transparency, integrity, proper citation, and responsible use of previously published data.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions
Conceptualization, methodology, review and editing: Seyed Sajad Mousavi and Mobin Ebrahimian; Supervision: Seyed Sajad Mousavi; Writing the original draft: All Authors.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgments
The authors would like to express their sincere appreciation to the Tehran Disaster Mitigation and Management Organization for their valuable collaboration and technical that supported the development of this study.