At Empa, the Swiss Federal Laboratories for Materials Science and Technology, Bernd Nowack and colleagues investigated potential hazards that follow the release of certain nanoparticles, especially nanobiomaterials in the environment. These materials are promising for nano medical applications and drugs. To access their risk the hazard potential and exposure needs to be determined. To map the risk of a substance the researchers map first the threshold at which the substance has no longer any harmful effect.   Below you find a copy of the predicted No-Effect Concentrations of various nanomaterials in fresh water (1).

Table: Predicted no-effect concentrations (PNEC) of nanobiomaterials (NBMs), engineered nanomaterials (ENMs), pharmaceuticals and some pollutants in freshwater (1).

As can be seen on the logarithmic scale nano-silver particles are one of the most toxic materials, more than Nano-Zinkoxide and Nano-TiO₂ that is often found in pigments for paints. The graph also reveals the literature findings for different common pollutants in comparison such as lead and mercury. In the original article (1) you will find the citations for the data points.

Source: https://www.empa.ch/web/s604/nanosafety

(1) Hauser, M., Li, G. & Nowack, B. Environmental hazard assessment for polymeric and inorganic nanobiomaterials used in drug delivery. J Nanobiotechnol17, 56 (2019).
https://doi.org/10.1186/s12951-019-0489-8