Emerging Contaminants in natural freshwaters of the Pacific Coast of South America: State of the Art and Recent Developments.

• synthesis of CEC´s patterns, water types, and regulatory and treatment constraints • identified lack of data on the CECs in waters in Ecuador, Peru, Colombia, Chile • CECs can be used as tracers of contamination origin and water residence times • CECs assess contamination pathways under extreme hydroclimatic conditions • CECs trace the consumption patterns of illicit drugs in highly populated areas This study presents a regional analysis of the state of the art and recent advances in the monitoring and research on Contaminants of Emerging Concern (CECs) in natural freshwater bodies of Latin America, focusing on the Pacific coast countries. Unlike larger nations like Mexico and Brazil, countries such as Colombia, Peru, Ecuador, and Chile are in an early stage of CECs monitoring with several new research challenges. The review addresses 39 studies monitoring the occurrence of main CECs categories, such as pharmaceuticals, pesticides endocrine disruptors, personal care products, and illicit drugs in surface water, groundwater, wastewater, drinking water and domestic water. The spatial distribution of sampling sites reveals that efforts are concentrated in urban and industrialized zones, while rural and remote areas remain underexplored. This uneven spatial distribution highlights the need to expand geographic coverage in future monitoring programs. The analysis also shows a lack of research on groundwater and specific ecosystems such as lagoons and estuaries, evidencing the need to expand research in these areas. Likewise, it was identified that CECs can be used as tracers for illicit drug consumption and the mobility of contaminants during extreme weather events. Finally, it was observed that the COVID-19 pandemic influenced the variation of some pollutants, which reinforced the link between consumption patterns and water pollution. This review underscores the need for more advanced, cost-effective treatment technologies for CEC removal and proposes research directions to enhance water resource management and protection in Latin America.