Triple threat: a review on nanoplastic ecotoxicity, pollutant co-exposures, and climate change in freshwater organisms

Plastic-waste pollution has become one of the major threats to the entire environment, including the aquatic ecosystems. Vast literature is available on microplastics ecotoxicity; however, further degradation leads to nano-sized plastics, or nanoplastics (NP), which were reported to be more reactive and even more toxic for the aquatic biota despite the fact that they were studied to a lesser extent. In a context of a changing world, where freshwater systems are particularly sensitive, and the ecotoxicology of plastic as a nanopollutant has been poorly addressed in comparison with the marine environment, the objective of this study is to evaluate the physiological effects in case of NP co-exposures with other pollutants and/or stressors, and also provide further insights into in a context of climate change (CC) based on peer-reviewed literature published between 2020 and 2025. The most represented groups were freshwater algae, microinvertebrate and fish; however, they were predominantly represented by a few model species: Chlorella spp. alga, Daphnia magna microcrustacean, and Danio rerio fish, respectively. Metals and pesticides were the most frequently studied co-stressors. Synergistic interactions emerged as particularly relevant, often linked to NP acting as pollutant vectors through Trojan horse-derived mechanism. Regarding CC, rising temperature was the most assessed variable, generally enhancing NP toxicity in freshwater organisms. Our findings highlight the complexity of realistic co-exposure scenarios and emphasize the need for ecotoxicological studies that address multiple stressors in a changing world.