Prioritization of contaminants of emerging concern in European surface waters using occurrence, exposure, prediction, and regulatory status perspectives

Contaminants of emerging concern (CECs) are increasingly detected in European aquatic environments, yet heterogeneous monitoring data, scarce toxicity information, and evolving regulatory frameworks limit their prioritization. This study developed an evidence-integrated multicriteria framework to prioritize CECs in European surface waters by combining occurrence, reported ecological risk, regulatory recognition, and QSAR-derived hazard & fate endpoints. From an initial list of 259 literature-relevant candidate contaminants, 45 CECs were retained after QSAR reliability filtering. Criteria were weighted using a hybrid AHP-CRITIC approach and ranked with PROMETHEE II. In the baseline model, risk quotient and detection frequency received the highest weights, indicating the strong influence of empirical risk and occurrence. Diuron, 17β-estradiol, tributyl phosphate, 4-n-octylphenol and 4-tert-octylphenol were the five highest-priority contaminants due to convergence of reported ecological risk with strong intrinsic hazard, particularly aquatic toxicity and bioaccumulation potential. Scenario-based sensitivity analysis showed that diuron, 17β-estradiol, 4-n-octylphenol, 4-tert-octylphenol and fluoranthene formed a consistent core priority group, while triclosan, butylated hydroxytoluene and propiconazole gained relevance under hazard-oriented configurations. None of the final 45 contaminants were included in Directive 2024/3019 relative to wastewater treatment plants due to lack of reliable toxicity data in the QSAR model, suggesting that the framework provides a complementary perspective to current European regulatory priorities. This approach supports transparent screening, monitoring design and anticipatory management of CECs in European surface waters.