Deriving marine metal water quality criteria for aquatic organisms in China: progress, gaps, and future directions

Abstract Water quality criteria (WQC) serve as the scientific foundation for protecting aquatic ecosystems and informing regulatory standards. Over the past decade, China has shifted from relying on foreign benchmarks to developing a more ecologically and regionally relevant WQC framework. This study reviews the technical framework, methodological advances, and current research on the development of marine WQC in China, focusing particularly on metals. In line with the marine technical guidelines from the Ministry of Ecology and Environment (MEE, HJ 1260–2022), China has officially adopted the species sensitivity distribution (SSD) approach as the national standard for criteria development. Key steps in the progress—including scoping, data acquisition, toxicity data preprocessing, model fitting, and criterion calculation—are detailed. Recent studies on lead (Pb), copper (Cu), cadmium (Cd), zinc (Zn), and nanosized metals demonstrate rapid methodological refinement, integrating international models such as the SSD, biotic ligand model (BLM), and multiple linear regression (MLR) with datasets from native species and local water chemistries. However, challenges such as limited chronic and early-life toxicity data for ecologically critical taxa, incomplete integration of toxicity-modifying factors (TMFs), and insufficient validation across diverse ecosystems remain. Future WQC development in China should be structured around three core elements: (1) Expanding chronic toxicity datasets for representative resident species and sensitive life stages; (2) incorporating TMF normalization using empirical and mechanistic approaches to generate chemistry-aware criteria; and (3) validating laboratory benchmarks under field-realistic conditions, supported by a curated national toxicity database. These advancements will enable China to produce WQC that are scientifically defensible, nationally applicable, and regionally adaptable, providing a robust foundation for sustainable aquatic management in an era of accelerating environmental changes.