The double-edged nanoparticle: remediation benefits vs. mechanistic toxicity risks in aquatic systems

Abstract

Engineered nanomaterials (ENMs) offer a double-edged sword for aquatic remediation: while serving as powerful agents for pollutant removal, their inherent reactivity creates significant ecotoxicological risks. This critical review deconstructs this duality by providing an integrated analysis of remediation benefits versus mechanistic hazards. It is argued that the physicochemical properties driving remedial function-such as high surface reactivity and redox potential-are the shared origin of the molecular initiating events of toxicity. For instance, while photocatalytic ENMs can achieve >90% degradation of recalcitrant organics, this same non-selective reactivity can trigger a 1.5-2-fold increase in intracellular ROS in non-target aquatic organisms. The analysis reveals how this relationship is dynamically modulated by environmental transformations (e.g., eco-corona formation, aggregation), creating profound challenges for conventional risk assessment. Consequently, a paradigm shift from a reactive, post hoc evaluation to a proactive safe-and-sustainable-by-design (SSbD) framework is advocated. This approach, which embeds mechanistic toxicology as an a priori design tool, is presented as the critical pathway to rationally decouple efficacy from hazard. Only through this integrated perspective can the transformative potential of nanoremediation for ensuring global water security be realised through sustainable design.