This study marks the first recorded case of TiO2 nanoparticle pollution in Chilean rivers, indicating significant progress in understanding the distribution of nanowaste and its effects on a global scale. By investigating four different locations, including the outlet of a wastewater treatment plant during summer, winter and spring, the research revealed varied concentrations of TiO2 nanoparticles, with a notable range between 17.6 µg L−1 during the summer and 22.9 µg L−1 in spring in downstream river sections. The study used transmission electron microscopy to characterize nanoparticles, observing sizes between 10 and 206 nm, and an EDS detector confirmed titanium proportions of 4.84 % to 20.35 % by dry weight. These TiO2 nanoparticles, predominantly in Rutile and Anatase forms, denote a significant environmental presence, especially considering the low population densities of the sampling areas. The findings highlight the urgent need for international awareness and routine monitoring of nanowaste, advocating for preventive actions in the production of nanomaterials and adaptive management strategies in tune with the dynamic nature of water systems and environmental changes, both for places densely and sparsely populated.