Organic contaminants of emerging concern in global estuaries: Environmental occurrence, fate, and bioavailability

Organic contaminants of emerging concern (OCECs) originating from assorted sources have attracted increasing attention latterly as most of them are not under routine surveillance or effective regulation but possess persistent, bioaccumulative, and toxic potential. Massive terrestrial inputs and proximity to intense human activities have elevated OCEC contamination in many estuaries. The present review outlines the current knowledge on the environmental occurrence and fate, as well as bioavailability of nine classes of OCECs, i.e., per- and polyfluoroalkyl substances, alternative halogenated flame retardants, organophosphate esters, chlorinated paraffins, ionic surfactants, phthalate alternatives, polyhalogenated carbazoles, synthetic antioxidants, and bisphenol A alternatives in global estuaries. Available data have documented prevalence of studied OCECs in estuarine compartments from around the world, particularly in North America, Europe, and Asia. Their spatiotemporal trends, vertical distributions in the water column, and multi-media partitioning are mainly dependent on anthropogenic impacts (e.g., production and consumption patterns, urbanization, industrialization, and waste treatment), hydrodynamics, meteorological conditions, characteristics of environmental media and the interactions with OCECs, and physiochemical properties of OCECs. Bioaccumulation and biomagnification have also been reported for many estuarine OCECs, which favor those with moderate hydrophobicity, considerable proteophilicity, and satisfactory resistance to environmental degradation and biological transformation. To comprehensively elucidate OCEC exposure for estuarine ecosystems from the big picture, future research is warranted in various fields, including environmental chemistry and (eco-)toxicology, and may involve more interdisciplinary collaborations.