There is an emerging concern about the potential health and environmental impacts of nanoplastics in the environment. Despite the lack of information on the exposure side, there is a growing number of ecotoxicological hazard data available which enable to conduct a hazard assessment for nanoplastics in freshwater and marine systems. Based on a critical evaluation of published studies and building probabilistic species sensitivity distributions (PSSDs), our work presents a comprehensive understanding of the state of art of nanoplastic ecotoxicity. Different freshwater and marine datasets were constructed based on different data quality levels and for each of the datasets, PSSDs were built for both mass- and particle number-based concentrations. Predicted no effect concentrations (PNECs) were then extracted from the PSSDs. Hereby, we report PNECs at 99 μg·L-1 and 72 μg·L-1 respectively for the freshwater and marine dataset after the removal of data measured in the presence of sodium azide (NaN3), which is considered to be a major interfering factor in the ecotoxicity testing of nanoplastics. By comparing the PNECs, we found that nanoplastics are less toxic than microplastics and many engineered nanomaterials. Besides, the effects of size and polymer type on the toxicity were also statistically tested. We observed that there is no significant difference in ecotoxicity for nanoplastics of different size while polystyrene nanoplastics were significantly more toxic than all other tested nanoplastics. In conclusion, the results presented in this work provide a comprehensive description of nanoplastic ecotoxicity based on the current knowledge. This work constitutes a fundamental step towards an environmental risk assessment for nanoplastics in freshwater and marine systems.