Increased use and production of different types of engineered nanoparticles (NPs) lead to an elevated risk of their diffuse dispersion into the aquatic environment and increased concern on unknown effects induced by their potential release into aquatic ecosystems. Such a risk is especially high for catalytically active materials with highly developed surfaces, easily available for the interaction with the environment. An improved understanding of the environmental transformation processes of NPs of various surface characteristics is hence imperative for risk assessment and management of production, use and disposal of NPs. This study presents results on effects of natural organic matter (NOM) and eco-corona biomolecules (EC) on the environmental transformation and dissolution of different types of inorganic engineered NPs of different surface and solubility properties in synthetic freshwater (FW) with and without NOM and EC. Surface transformation and dissolution of NPs was shown to be dependent on exposure and time and specific depending on the surface and the environment. For instance, the adsorption of NOM on the surface of the studied NPs resulted in the formation of negatively charged colloids of higher stability and smaller size distribution compared with the same NPs in FW only. The dissolution rate of the NPs in the presence of NOM correlated with the strength of interactions between the carboxylate group of NOM and the particle surface. However, no general correlation was observed between dissolution, particle types, surface conditions, and EC/NOM adsorption, emphasizing the need for thorough investigations to develop relevant protocols and guidelines. It was further shown that the presence of NOM reduced the ecotoxic potency of the NPs by decreasing the intracellular reactive oxygen species generation and, in some cases, reducing their cytotoxicity, which can be attributed to the stronger interaction of carboxylate groups of NOM with the surface of the NPs. This underlines the importance of thorough investigations of adsorption/ desorption, degradation, and exposure scenarios for NPs with in order to develop regulatory relevant protocols and guidelines. An improved understanding of the environmental transformation processes of NPs, particularly in relation to NOM and EC, will help to guide risk assessment and management efforts towards promoting sustainable development and minimizing harm to the ecosystem.