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Impact of aged and virgin polyethylene microplastics on multi end-points effects of freshwater fish tissues
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Freshwater fish exposed to polyethylene microplastics for 15 days showed increased oxidative stress in both liver and muscle tissue, with aged, UV-weathered microplastics causing more damage than new ones. The weathering process changed the plastic surface in ways that made the particles more chemically reactive and potentially more harmful. This matters because microplastics in the environment are typically aged, meaning lab studies using only pristine particles may underestimate real-world toxicity.
The buildup of plastic waste in aquatic environments presents serious threats to the environment, wildlife, and ultimately to humans. Specifically, microplastics (MPs) ingestion by aquatic animals leads to adverse physiological and toxicological effects. In addition, discarded MPs undergo aging and degradation processes which affect their morphological properties and chemical composition, enhancing the absorption of environmental pollutants. Under this prism, the present research was conducted to investigate and compare the impact of 'aged' versus pristine low-density polyethylene microplastics (PE-MPs) on various toxicity endpoints as biochemical and molecular parameters in the muscle tissue and liver of the freshwater fish species Perca fluviatilis. In parallel, the morphological, physicochemical, and structural changes occurred in "aged" PE-MPs, (after being exposed to UV radiation for 120 days) were studied, significantly illustrating signs of oxidation and crack propagation at the surface of the studied MPs. Fish were exposed to artificial diet reached with virgin and "aged" PE-MPs, sized 100-180 μm, at concentrations of 1 mg/g of dry food for a period of 15-days. Thereafter, liver and muscle tissues were analyzed in relation to multi oxidative parameters. Compared to the control group, the observed changes in the examined fish included increased activities of antioxidant enzymes, as superoxide dismutase, catalase and glutathione reductase, enhanced concentrations of malondialdehyde, protein carbonylation, HSP70 levels, elevated MAPK phosphorylation, induction of ubiquitin-proteins, as well as heightened levels of Bax/Bcl-2 proteins, caspases and differentiated levels of LC3 II/I, SQSTM1/p62. From the studied biomarkers, apoptosis, ubiquitin and hsp70 levels, showed a more sensitive response against the ingested MPs, followed by autophagy, p38MAPK levels, antioxidant enzymes, MDA and carbonylation levels. The effect of "aged" PE-MPs was more pronounced compared to that of the virgin ones. When evaluating the response of all oxidative stress biomarkers across the studied tissues, the liver demonstrates the highest response for the majority of the biomarkers against both virgin and "aged" PE-MPs. These findings strongly indicate that "aged" MPs activate the antioxidant defence mechanisms and impact the cellular well-being of the examined fish species.
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Oxidative and inflammatory responses to virgin and beached microplastics in marine fish liver
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This study compared oxidative stress and inflammation responses in marine organisms exposed to virgin microplastics versus weathered, beach-collected microplastics. Beached particles, which have undergone environmental aging, triggered different and in some cases stronger toxic responses than their pristine counterparts.
Oxidative and inflammatory responses to virgin and beached microplastics in marine fish liver
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This study compared oxidative stress and inflammatory responses in marine fish exposed to virgin versus beached, weathered microplastics, finding that aging changes particle toxicity. Beached microplastics triggered stronger or qualitatively different inflammatory responses than their pristine counterparts, underscoring the importance of using environmentally realistic particles in toxicity studies.
Genotoxicity and metabolic changes induced via ingestion of virgin and UV-aged polyethylene microplastics by the freshwater fish Perca fluviatilis
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Freshwater perch fed UV-aged polyethylene microplastics showed greater DNA damage and more severe metabolic disruption in liver and muscle tissue than fish fed virgin (new) microplastics. The aged plastics disrupted energy metabolism, amino acid processing, and neurotransmitter levels. Since most microplastics in the environment have been weathered by sunlight, these findings suggest the real-world health risks to fish — and potentially to the humans who eat them — may be greater than lab studies using fresh plastics indicate.
Impact of virgin and weathered microplastics on zebrafish: Bioaccumulation, developmental toxicity and molecular pathway disruptions
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Researchers compared the effects of brand-new versus environmentally weathered microplastics on zebrafish larvae and found that weathered particles were far more toxic, causing 80% mortality compared to 20% for new plastics. The weathered microplastics triggered more severe disruptions to oxidative stress pathways, cell death signaling, and DNA repair mechanisms. The study emphasizes that laboratory tests using only pristine microplastics may significantly underestimate the real-world dangers of plastic pollution.
Oxidative aging facilitates biological barrier penetration of polyethylene microplastics, amplifying systemic lipotoxicity in aquatic species
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When plastic waste breaks down in the environment, sunlight and weathering "age" microplastics, making them more chemically reactive—and this study found that aged microplastic particles are far more harmful than fresh ones. In tests on water fleas and zebrafish embryos, these aged particles slipped past protective barriers (like an egg's outer shell) more easily, disrupted fat metabolism, and slowed heart rates. This matters because most safety research uses "pristine" microplastics, so real-world risks—including potentially to human health, since we're also exposed to weathered plastic particles in water and food—may be underestimated.
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