On February 24, 2022, the European Union (EU) Observatory for Nanomaterials (EUON) published a Nanopinion entitled “Are nanoplastics hazardous? The way forward to overcome the uncertainties of risk assessment” by Dr. Anita Jemec Kokalj and Dr. Dana Kühnel about defining the criteria to evaluate which properties of nanoplastics should be reported in future studies to decrease uncertainties in their risk assessment. The authors state that nanoplastics “are complex environmental pollutants that come in multiple shapes, sizes, colours and polymer compositions.” According to the authors, there are currently two main uncertainties for the environmental risk assessment of nanoplastics: the challenging sampling situation in the environment and the subsequent risk quantification; and that the majority of current ecotoxicity studies investigate laboratory-produced primary nanoplastics with well-defined properties. The authors note that these latter studies do, however, enable the development of guidelines for further research on secondary nanoplastics. Existing research with primary nanoplastics can be used as a model to define the criteria to evaluate which physico-chemical properties of nanoplastics should be reported in future studies. The authors suggest that “once further refined, the existing study quality assessment originally developed for nano(eco)toxicity studies can now be applied to nanoplastics studies, with a further outlook for microplastics.” This will allow better comparisons across different studies and more relevant parameters to be reported. The authors conclude that “[o]verall, this will help decrease uncertainties in risk assessment, as the relevant parameters for nanoplastics exposure, fate and hazard assessment will be better defined in the future.”