The European food production system has historically focused on increasing agricultural output. However, a shift towards a circular economy is underway, driven by initiatives like the Green Deal and Farm-to-Fork strategy, aiming to reduce food waste and utilize side streams more effectively. While this transition offers environmental and socio-economic advantages, it also raises crucial food safety concerns. Reusing by-products, which lack a history of safe use in food production, introduces potential hazards. These hazards might manifest at unexpected stages in the production process or involve newly introduced contaminants. Furthermore, the closed-loop nature of circular systems can lead to the accumulation of low-level contaminants, potentially reaching unsafe levels in final food products. Therefore, maintaining current food safety standards while transitioning to a circular economy is a significant challenge. This research addresses this challenge by developing a framework for a priori assessment of food safety risks during the transition to circular food production systems in Europe, based on Hazard Analysis Critical Control Points (HACCP) principles and adhering to the General Food Law (EC/2002/178). The framework analyzes the entire supply chain, not just individual food business operators (FBOs).

Existing literature highlights the growing interest in circular food systems and their potential environmental and economic benefits. Several studies have investigated the impact of circular economy approaches on various aspects of agriculture and food production. Research on the use of insect-based protein as an alternative food and feed source is also rapidly expanding. Existing studies on food safety within circular systems are still limited. This gap in knowledge necessitates the development of a robust framework for systematically assessing and managing food safety risks associated with the transition to circular production. The current research builds upon existing HACCP principles and EU food safety regulations to provide a comprehensive approach to food safety risk assessment within the context of circular food systems.

The study proposes a three-step framework for evaluating food safety in circular food systems (Fig. 1): **Step 1: Describing Supply Chain Changes:** This step involves a detailed description of the current (linear) food supply chain, identifying its stages, processes, and material flows. Then, the proposed changes to create a circular system are incorporated, analyzing how these modifications alter the chain's stages, processes, and flows. This requires expertise from various stakeholders in the supply chain. **Step 2: Identifying Potential Food Safety Hazards:** Closing production loops can lead to the accumulation of known hazards or the introduction of new ones. This step involves creating a comprehensive list of potential microbiological and chemical hazards using systematic reviews, expert elicitation studies, or a combination of both. The chosen method depends on data availability and resources. **Step 3: Prioritizing Food Safety Hazards:** This step involves ranking hazards based on their potential human health risks. The framework adopts a semi-quantitative approach, classifying factors into low, medium, and high categories, acknowledging the scarcity of data on the impacts of circularity on food safety. The assessment considers two key aspects: the presence of hazards in final food products and their health effects. The presence is determined by analyzing the occurrence of hazards in raw materials, their persistence in the environment, and their transfer to edible plant or animal parts. Health effects are evaluated using available health-based guidance values (e.g., ADI, TDI, DALY) for both chemical and microbiological hazards. Finally, a combined risk score is created to prioritize the hazards (Table 9). Three case studies were conducted to test the framework.

The framework was applied to three case studies: **Case Study 1: Animal Manure in Agriculture:** This study examined the use of animal manure as fertilizer in horticulture, focusing on the presence of antibiotics and pathogens (*Salmonella*, *E. coli*) in manure and their transfer to crops. Findings indicated that (fluoro)quinolones posed the highest risk due to high occurrence, persistence, and severity. (Table 1, 2, 3) **Case Study 2: Side Streams for Insect Rearing:** This study analyzed the use of household waste and animal manure as substrates for rearing black soldier fly (BSF) larvae. The focus was on chemical contaminants (dioxins, PCBs, mycotoxins, pesticides, heavy metals). Results showed that cadmium and lead presented the highest risks due to high accumulation in BSF larvae and high toxicity (Table 5). **Case Study 3: Local Production/Shorter Supply Chains:** This study compared mycotoxin contamination in locally produced wheat flour versus conventionally produced flour. The analysis showed that while average mycotoxin concentrations were similar, the short-chain scenario had a higher likelihood of exceeding regulatory limits due to the lack of mixing of batches from different fields. (Table 6, 7, 8) Overall, the case studies consistently demonstrate that the transition to circularity primarily affects the occurrence of food safety hazards, rather than their severity, highlighting the importance of focusing on indicators related to hazard presence and transfer.

The developed framework provides a valuable tool for identifying and prioritizing food safety hazards during the transition to circular food systems. The semi-quantitative approach, using low, medium, and high classifications, is suitable for situations with limited data, a common challenge in emerging systems. The case studies illustrate the applicability of the framework across different circularity strategies. The results consistently indicate that changes in the presence of hazards are more critical than changes in their severity. This underscores the importance of focusing on indicators like occurrence, persistence, and transfer when assessing food safety risks in circular food systems. While the framework provides a useful starting point, further refinement is needed, particularly in defining more precise thresholds for hazard classification and incorporating more quantitative data as they become available.

This study presents a novel framework for identifying and prioritizing food safety hazards in the transition to circular food systems. The framework, tested through three case studies, effectively identifies and prioritizes hazards based on their presence in final food products and health effects. The findings highlight that circularity primarily impacts the occurrence of hazards, underscoring the need for focusing on indicators of hazard presence and transfer. This framework provides a practical tool for risk managers and researchers, guiding efforts to ensure food safety during the shift towards more sustainable and circular food production systems. Further research should focus on refining the framework's quantitative aspects and expanding its application to a wider range of circular food systems.

The study's semi-quantitative nature, necessitated by data limitations, introduces subjectivity in hazard classification. The case studies, while illustrative, represent a limited range of circular food systems. Further research is needed to validate the framework's applicability across diverse contexts and to refine the classification thresholds using more comprehensive data sets. Furthermore, the framework primarily focuses on human health risks, while environmental impacts are not fully considered.