Deep eutectic solvents (DESs) are a relatively new type of solvent that have attracted the attention of the scientific community due to their environmentally friendly properties and their versatility in many applications. Many possible DESs have been described and, thus, it is not easy to unequivocally characterize and generalize their properties. This is especially important in the case of the (eco)toxicity information that can be found for these mixtures. In this review, we collect data on the human and environmental toxicity of DESs, with the aim of gathering and exploring the behavioral patterns of DESs. The toxicity data found were analyzed attending to different factors: hydrogen bond donors or acceptors that form part of the eutectic mixture, pH, and the presence of organic acids in the DES molar ratio of the components, or interactions with natural compounds. In the case of ecotoxicity, results generally depend on the biomodel studied, along with other factors that have been also revised. Finally, we also carried out a revision of the biodegradation of DESs.

In the last half century, the improvements in quality of life owing to the development of the chemical industry are indisputable. However, despite global improvements, there has also been a large increase in pollution at the environmental level and this has caused relevant harmful risks not only to wildlife and the environment but also to human health. In response, governments have begun to regulate and control chemicals to prevent environmental pollution. At the European level, REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) was created with the aim to protect human/animal health and the environment from chemicals. Additionally, this regulation shows the main experimental tests that are needed to classify a chemical from a physicochemical and toxicological point of view. The main objective of this study is to compare the tests or experiments stipulated by the European REACH regulation with the studies carried out by the scientific community. To obtain this comparison, an exhaustive bibliographic review was carried out, analyzing the physicochemical properties and the (eco)toxicological information established by the European REACH regulation and scientific articles published in the Web of Science (WOS) database. The results obtained indicate that, although there are many authors who conducted tests indicated by the regulation, there are others whose essays or studies are not in line with the regulation; this may be because, on many occasions, the purpose of the information to be obtained is quite different.