The European Union (EU) Observatory for Nanomaterials (EUON) announced on December 12, 2022, the results of a desk study entitled Study on (bio)degradation, persistence and safe by design of nanomaterials. The study aimed at providing information on the state of the art, the existing gaps, and the research needs for the (bio)degradation and persistence of nanomaterials and their relevant organic coatings. Another objective was to examine the current state of the art for safe by design (SbD) nanomaterials as it relates to the degradation and persistence of nanomaterials. According to EUON, the study found that work on the (bio)degradation of nanomaterials focuses mainly on carbon-based and organic nanomaterials, many of which more easily degrade compared to inorganic nanomaterials, although certain organic nanomaterials are very persistent as well. Certain organic nanomaterials (e.g., biopolymers, lipids) are the easiest to degrade, while carbon-based nanomaterials are more persistent in vivo. The study notes that most of the test guidelines used for studying the degradation and persistence of chemicals have been applied to nanomaterials, with or without modifications. There is a lack of consensus on how to define SbD nanomaterials, mostly due to the vagueness of the term “safety” itself, but also because of the unique nature of nanomaterials and their different properties. The study found proposed SbD strategies that are already available for nanomaterials. Of interest, according to EUON, is the concept of “safe-by-degradation,” which implements the concept of the optimized lifetime of a nanomaterial to SbD, including its safe clearance from the body and the environment. In the case of carbon nanotubes (CNT), it has been suggested that decreasing their length leads to decreased toxicity, although this approach is not able to eliminate fully any adverse effects. EUON notes that in the expert survey complementing the study’s literature search, 30 percent of the survey participants suggested that the sustainability domain should be part of the SbD framework and should specifically integrate the environmental and societal dimension.