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Multi-level approach to evaluate the toxicity of virgin and weathered microplastics made of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) on Daphnia magna
Summary
Researchers assessed the toxicity of both virgin and weathered bioplastic microplastics using a multi-level approach including biomarkers of oxidative stress and cellular damage. Weathered bioplastics showed altered toxicity compared to virgin material, demonstrating that environmental aging affects the hazard posed by biodegradable alternatives.
Like conventional plastics, at end-life bioplastics can enter and contaminate ecosystems. Once in the environment, bioplastics can undergo different weathering processes, which can lead to the production of microplastics (MPs) having variable chemical-physical features and representing a threat for organisms. The aim of this work was to investigate the potential adverse effects induced by the exposure to virgin and weathered MPs obtained from bioplastic objects made of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) towards the cladoceran Daphnia magna. Virgin MPs were obtained from PLA-based disposable knifes and PBAT-based shopping bags. Weathered MPs were obtained following the ISO 4892-2 regulations placing Virgin MPs inside a solarbox. Organisms were exposed for 21-days to three concentrations (0.125 µg/mL, 1.25 µg/mL, 12.5 µg/mL) of virgin and weathered PLA-MPs or PBAT-MPs. A multi-level approach was performed to investigate adverse effects at different levels of the biological hierarchy, from sub-individual (molecular and biochemical) to individual (growth rate and behavior) level. At molecular level, the modulation of the expression of different genes involved in oxidative stress (cat and sod), physiological and behavioral pathways (flot, SERCA and JHE) was assessed. At biochemical level the onset of oxidative stress (activity of antioxidant and detoxification enzymes, lipid peroxidation) was explored. Modulations in proteins, carbohydrates and lipids content, as well as in the total caloric content, were also investigated to check for alterations in energy reserves. Changes in growth rate, swimming activity and reproductive efforts were investigated to assess effects at individual level. Our results showed that the exposure to MPs obtained from bioplastics, both virgin and weathered, induced effects at sub-individual and individual levels, suggesting the necessity to study the potential toxicity of bioplastics due to their degradation in environment. Also see: https://micro2024.sciencesconf.org/559511/document