KIU Publications

Transformation products (TPs) of emerging contaminants are emerging as a major frontier in environmental chemistry, toxicology, and regulatory science because many exhibit greater persistence, mobility, bioavailability, or biological activity than their parent compounds. These transformation-driven changes can alter exposure pathways, trophic interactions, environmental transport, and long-term ecological and human health risks, challenging conventional parent-compound-centered approaches to chemical risk assessment. This review critically examines the formation path ways, environmental fate, analytical detection, predictive modeling, and regulatory implications of TPs derived from major contaminant groups, including pharmaceu ticals, pesticides, industrial chemicals, plastic additives, and per- and polyfluoroalkyl substances (PFAS). Unlike many existing reviews that focus primarily on TP occur rence, analytical detection, or individual contaminant classes, this review advances a transformation-aware predictive systems framework that integrates formation mechanisms, environmental fate, analytical monitoring, predictive modeling, toxicity assessment, and regulatory decision-making into a unified risk-governance approach. Evidence from the reviewed literature shows that selected pharmaceutical, pesticide, PFAS-related, and plastic-associated contaminants and their transformation products are commonly detected in wastewater, surface water, groundwater, drinking-water systems, sediments, and biological matrices, with reported concentrations often rang ing from ng/L to µg/L levels depending on contaminant class, matrix, source intensity, and treatment conditions. Particular attention is given to coupled biotic and abiotic mechanisms governing TP formation, including microbial metabolism, photochemical reactions, hydrolysis, oxidation–reduction processes, and treatment-induced transfor mations across aquatic, terrestrial, atmospheric, indoor, and engineered systems. The review further evaluates how physicochemical properties influence TP persistence, partitioning, trophic transfer, bioaccumulation, and long-range transport. Advances in high-resolution mass spectrometry, suspect and non-target screening, isotope assisted pathway tracing, and machine-learning-assisted prediction are discussed as transformative tools for identifying overlooked contaminants and anticipating transformation-driven risks. Persistent regulatory blind spots are critically examined, particularly the limited incorporation of TPs into monitoring frameworks, exposure modeling, watch-list systems, and chemical governance. In response, the review pro poses an integrated monitoring–modeling–toxicity–policy pathway to support adap tive environmental risk governance. Recognizing TPs as independent environmental risk entities rather than secondary degradation byproducts represents a necessary par adigm shift for advancing chemical safety assessment, sustainable pollution manage ment, and proactive environmental protection in the era of emerging contaminants.