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Comparison of the Potential Chronic Toxicity of Polypropylene and Polylactic Acid to the Amphipod Gammarus Aequicauda
Summary
Researchers compared the chronic toxicity of conventional polypropylene (PP) and biodegradable polylactic acid (PLA) microplastics on the marine amphipod Gammarus aequicauda to assess whether bioplastics are a safer alternative. The study found that both polymer types caused harm to this crustacean, indicating biodegradable plastics are not necessarily benign once released into marine environments.
Plastic pollution is known to be a significant human-caused environmental hazard. Plastic persists and accumulates in coastal and marine ecosystems around the world, affecting their structure and function, and consequently the services they provide. The increasing demand for eco-friendly alternatives to conventional plastics has led to the development of biodegradable polymers. Although these polymers degrade more easily than traditional plastics under certain conditions, they can still end up in the environment if not managed properly. The ecotoxicological effects of bioplastics on the marine biota are still scarce and limited. This study compared the sublethal effects of the biodegradable polymer polylactic acid microplastics (PLA MPs) and non-biodegradable polymer polypropylene microplastics (PP MPs) on the marine amphipod Gammarus aequicauda. Juvenile amphipods (2–4 mm) were exposed to 5 mg/L of PLA and PP MPs (38–212 µm) obtained from commercial cups, in a chronic exposure (60 days) to assess their effect on the growth (assessed by measuring the head length and counting the number of articles of the first antennae) and fertility (reproduction, embryonic development, newborns per female and aborted eggs). The results showed that both PLA and PP MPs significantly slowed the growth and impaired the reproductive fitness in G. aequicauda. The effects trends were similar for both polymers (PLA and PP) and only in a few cases did they show significant differences between them. However, conventional PP MPs were always found to be slightly more toxic than the PLA MPs. At the end of the chronic exposure period, the control amphipods had grown by 260% compared to the time 0, while those treated with MPs had grown by 223% and 197% for PLA and PP, respectively. The new-borns per female were 17.1 ± 3 in the control group and 10.5 and 9.8 in the PLA and PP MPs exposed groups, respectively. Furthermore, here for the first time the expression levels of seven genes involved in stress responses, were followed by Real time qPCR, to identify the molecular targets of PLA and PP. Molecular results supported the chronic toxicity showing an up-regulation of genes. Funding: This work was realised in the framework of BIOPLAST4SAFE project “Biomonitoring of biodegradable micro and nanoplastics: from the environment to humans in a one health perspective (Biomonitoraggio di micro e nanoplastiche biodegradabili: dall’ambiente all’uomo in una prospettiva one health) with the technical and economic support of the Italian Ministry of Health–PNC funds.