IN-DEPTH ECOTOXICOLOGICAL ASSESSMENT OF EMERGING CONTAMINANTS IN THREE MODEL SPECIES: A FOCUS ON PERFLUOROALKYL SUBSTANCES (PFAS) AND A NEGLECTED FLUOROQUINOLONE

The exponential socio-economic advancements of the past century have led to profound improvements in human well-being, impacting both industry and healthcare. However, this rapid progress has also led to the extensive production of various compounds, including synthetic chemicals for industrial applications, agrochemicals, and pharmaceuticals, often without a thorough understanding of their toxicological risks. Many of these substances have emerged as potential threats to both ecosystem integrity and human health. Environmental contamination only began attracting significant attention towards the end of the last century, as toxicological effects observed in humans were increasingly linked to chemical exposure. As a response, the scientific community embarked on a mission to unravel the harmful effects of these compounds on living organisms. A particular area of attention has emerged around Contaminants of Emerging Concern (CECs), substances recently detected in the environment or whose harmful effects have only recently been uncovered. Among CECs, per- and polyfluoroalkyl substances (PFAS) and antibiotics, particularly those within the fluoroquinolone (FQs) class, are the most prominent. PFAS, which have been produced since the 1940s, were not identified as environmental contaminants until the late 1990s. Since then, a growing weight of evidence has confirmed their toxicity. Despite this, only a limited number of these compounds have been subjected to regulatory restrictions, while newer-generation PFAS remain largely not regulated due to the lack of comprehensive toxicological data. Similarly, FQs antibiotics have been in production since the 1970s, starting with flumequine (FLU). Over time, increasingly potent formulations have been developed to combat bacterial infections in humans and animals alike. However, certain FQs have been banned due to severe side effects reported in humans and model species. Interestingly, the use of FLU in human medicine has been restricted by the European Medicines Agency (EMA); nevertheless, it is still used in livestock farming, raising concerns about its environmental spreading. Indeed, although FLU was the first FQ introduced to the market, has not been thoroughly investigated for its potential toxic effects on non-target species. In this study, the toxicity of these fluorinated compounds was explored on model organisms of both soil (Eisenia foetida) and freshwater ecosystems (Raphidocelis subcapitata and Daphnia magna), providing useful toxicity data where gaps exist. Beyond traditional acute and chronic toxicity tests, we employed cutting-edge techniques to assess sub-lethal effects, confirming the remarkable efficacy of these innovative methods in detecting subtle toxicological effects on non-target organisms. Our results indicate that new-generation PFAS exhibit toxic effects comparable to those of their now-banned predecessors. Additionally, we found that FLU, even at environmentally relevant concentrations, can trigger transgenerational effects in microcrustaceans, potentially threatening the survival of this crucial trophic level, and thus possibly endangering freshwater ecosystems.