Per- and polyfluoroalkyl substances (PFAS) are a class of over 4,700 synthetic chemicals, known for their high thermal and chemical stability, as well as hydrophobic and oleophobic properties. These features have led to their widespread use in products such as non-stick coatings, firefighting foams, and waterproof textiles. However, their extensive use has caused continuous release into the environment, making them ubiquitous in all environmental compartments. Due to their proven risks, some conventional PFAS have been banned and replaced by newer compounds, which are presumed to be less harmful. Nevertheless, studies on the effects of these substances on organisms and humans remain limited.

This study aimed at assessing and comparing the potential adverse effects induced by a 21-day exposure to a conventional (PFOA) and three emerging (ADV MFS-N2, ADV MFS-N3, and ADV MFS-M3) PFAS on the cladoceran Daphnia magna. Organisms were exposed to three environmentally-relevant concentrations (150, 1500, and 3,000 ng/L).

Effects were evaluated at both sub-individual and individual levels, including energetic (total caloric content) and oxidative stress related (activity of antioxidant and detoxifying enzymes, lipid peroxidation) biomarkers, morphological traits (e.g., head, spine, carapace, valve, and total body length), swimming behavior and survival. Results showed negligible effects after PFOA exposure, limited to a reduction in total body length. In contrast, exposure to ADV MFS-N2, ADV MFS-N3 and ADV MFS-M3 induced significant negative effects across multiple endpoints. Exposure to ADV MFS-N2 and ADV MFS-N3 exerted negative effects on the considered biochemical biomarkers and morphological traits. Whereas ADV MFS-M3 modulated the swimming behaviour of the exposed organisms. 

These findings highlight the urgent need for further research on the environmental fate and toxicity of emerging PFAS alternatives, which may pose a risk to aquatic ecosystems.