LIQUID PLASTICS AS A NEW ENVIRONMENTAL PROBLEM? AN INTEGRATED RISK ASSESSMENT OF POLYVINYL ALCOHOL, POLYETHYLENE GLYCOL, POLYVINYL PYRROLIDONE AND POLYACRYLIC ACID

Water-soluble polymers (WSPs), also known as "liquid plastics," are synthetic polymers that dissolve, disperse, or swell in water due to their hydrophilic groups. Despite their extensive use in various industrial and domestic products, these polymers are not currently regulated under European plastic strategies or chemical regulations, resulting in their pervasive presence in aquatic ecosystems. This study aimed to evaluate the ecotoxicity of four commonly used WSPs—polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and polyacrylic acid (PAA)—using the freshwater fish Danio rerio and the crustacean Daphnia magna as model organisms. The impacts were assessed at multiple levels of biological organization, including molecular, cellular, physiological, organismal, and population levels. Firstly, the study focused mainly on PVA standard, examining its acute and chronic effects on D. rerio and D. magna. Acute toxicity tests showed no significant effects at environmentally relevant concentrations, while chronic toxicity assessments revealed few behavioral changes in both D. magna and D. rerio, with slight enhancements in swimming performance under certain conditions. Subsequent studies expanded to include PVP, PEG, and PAA, uncovering significant dose-response relationships and behavioral alterations in D. rerio under varying light conditions. Proteomic analyses indicated that PVP had the most substantial impact on D. rerio embryos, followed by PEG and PAA, affecting genetic processes, signalling pathways, and eye development. In D. magna, PEG exhibited acute toxicity at 0.5 mg/L, while PVA notably impacted the proteome, altering proteins involved in stress responses, reproduction, and energy allocation. Biomarker analyses highlighted biochemical and physiological effects, with changes in heart rate and acetylcholinesterase activity. Behavioral assessments indicated stress responses in swimming patterns, suggesting potential ecological implications. To investigate the possible long-term and hereditary effects, the transgenerational impacts of PEG and PVA were evaluated on D. magna. This study revealed two generational effects, such as changes in DNA methylation and juvenile counts, which were significative between the F0 and F1 generations. However, these changes did not persist through the F4 generation, indicating that the induced epigenetic modifications were not heritable over multiple generations. Our findings underscore the necessity for comprehensive environmental assessments to evaluate the ecological risks associated with WSPs. This multi-level and integrative approach provided a detailed ecotoxicological profile of these WSPs, laying a foundation for future studies on their long-term and transgenerational effects. Additionally, studies focusing on their effects across different ecosystems—including terrestrial and marine environments—are necessary to obtain a complete understanding of their ecological impact.