Wastewater, industry, runoff, and degraded plastics pathways spread microplastics into waterways, and coastal areas. Lagoons, estuaries, and river systems, as semi-enclosed and ecologically sensitive environments, thus become prime reservoirs for their accumulation, increasing the risks to aquatic biodiversity and, indirectly, to human health. In this context, the International Atomic Energy Agency (IAEA) has, since 2024, strengthened its efforts through the NUTEC Plastics program, aimed at structuring an international network of laboratories, harmonizing analytical protocols, and developing next-generation detection technologies, ranging from satellite imagery integrated with artificial intelligence to spectroscopic approaches and advanced sensors. At the same time, nuclear techniques, and in particular radiotracing, are opening up new perspectives for monitoring in real time the transport, accumulation, and excretion of microplastics in aquatic and biological environments, through the use of radiolabeled plastics and non-destructive analyses. However, challenges remain, notably the stability of isotopes in saline and pH-varying environments, which can compromise the reliability of in situ measurements. This work highlights these recent advances and limitations, while emphasizing the potential of nuclear approaches, integrated with emerging technologies, to trace the fate of microplastics from urban effluents to sensitive coastal ecosystems. This synergy paves the way for more precise monitoring and a better understanding of the ecological and health impacts linked to plastic pollution.