Hazard- vs. Risk-based paradigms in agricultural water reuse: A global comparative analysis of regulatory frameworks

Irrigation with reclaimed wastewater is key for addressing water scarcity, but managing its environmental and health-related risks requires effective regulatory frameworks. As reuse policies expand globally, risk management approaches remain highly diverse due to differing socio-economic contexts. This review provides a comparative analysis of nine internationally influential agricultural water reuse policies (including European Union Regulation 2020/741, ISO 16075 standards, California Water Recycling Criteria, and Israel Inbar Regulations), examining how their design is shaped by the underlying risk management paradigms. The analysis distinguishes between hazard-based, risk-based, and hybrid regulatory approaches, including the use of fixed prescriptive standards, multiple-barrier strategies, and use restrictions based on water quality. This paper analyzes how risk management approaches dictate treatment requirements, quality thresholds, monitoring intensity, and implementation costs. Results demonstrate that regulatory outcomes are driven primarily by risk management philosophy and socio-economic context, rather than uniform scientific evidence. The review highlights that regulatory effectiveness depends on balancing safety standards with feasibility and practical enforceability. Overly restrictive, end-of-pipe compliance frameworks increase infrastructure costs and, by exceeding local feasibility, may inadvertently drive hazardous, unplanned reuse practices. Conversely, too flexible, fully-risk-based approaches are difficult to enforce and may fail to build public trust. Recent policy developments reveal a convergence toward hybrid regulatory approaches that combine baseline quality benchmarks with flexible, field-level risk mitigation measures such as subsurface drip irrigation and crop restriction. By clarifying how risk management paradigms shape agricultural water reuse regulations, this work provides insights to support the design of realistic and context-appropriate reuse policies.