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P05 | Combined Embryotoxic Effects of Microplastics and Heavy Metals in Xenopus Laevis
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Scientists exposed frog embryos to microplastics and heavy metals like cadmium, copper, and lead—both alone and combined—to see how these common water pollutants affect development. They found that the combo caused more harm than either pollutant alone, leading to birth defects, cell damage, and disrupted genes needed for healthy growth. While this study was done in frogs, it's a warning sign: microplastics may make other pollutants more dangerous, which matters since both are widespread in our water and food supply.
Microplastic particles, smaller than 5 mm, have been detected in humans and in marine and freshwater environments [1]. Due to their ability to bioaccumulate and biomagnify across trophic levels, they may seriously harm both humans and aquatic organisms [2]. In freshwater ecosystems, microplastics frequently co-occur with heavy metals (HMs), raising important environmental concerns [3]. However, the effects of combined exposure, often more toxic than single contaminants, remain poorly understood. In this study, we investigated the developmental toxicity induced by single and combined exposure to cadmium, copper, and lead together with 5 μm aged polystyrene microbeads (PSMBs), used to better mimic environmental conditions, in embryos of the model organism Xenopus laevis. This species is widely considered an excellent model for studying embryonic development in higher vertebrates. A multi-endpoint approach was employed, including a FETAX assay to evaluate mortality, growth, and malformations, together with histological and molecular analyses. Although mortality rates remained around 20%, except in cadmium-exposed groups, a high incidence of malformations was observed. Embryos exhibited craniofacial abnormalities involving the first and second branchial arches, intestinal malrotation, mucosal damage, altered pigmentation, and diffuse edema. Furthermore, exposure to these contaminants induced oxidative stress and increased apoptosis, particularly in embryos exposed to mixtures of metals and HM+PSMB combinations. Significant dysregulation of key developmental genes (otx2, pax6, sox3, sox9, egr2, bmp4, fgf8) was also detected and correlated with the observed malformations. In addition, genes associated with apoptosis (p53 and p65) and cellular detoxification (abcb1) showed marked alterations in expression, especially after combined exposures. Overall, our findings demonstrate that microplastics induce physiological stress during early development and exacerbate the bioaccumulation and toxicity of coexisting contaminants in aquatic organisms⁴. These results highlight the importance of evaluating microplastics within complex environmental contaminant mixtures.
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Developmental toxicity of co-exposure of heavy metal and polystyrene microplastics in Xenopus laevis embryo
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Researchers exposed Xenopus laevis frog embryos simultaneously to cadmium, copper, lead, and polystyrene microbeads, finding that co-exposure produced more complex effects than any single contaminant and that interactions included antagonistic as well as additive outcomes.
Toxicity assessment of polyethylene microplastics in combination with a mix of emerging pollutants on Physalaemus cuvieri tadpoles
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Researchers assessed the toxicity of polyethylene microplastics alone and in combination with a mixture of emerging pollutants on tadpoles of the frog Physalaemus cuvieri over 30 days. They found that combined exposure produced more severe effects on biomarkers related to oxidative stress and morphological development than individual exposures. The study highlights the need to consider how microplastics interact with other environmental contaminants when evaluating risks to amphibian populations.
Combined Effects of Microplastics and Mercury on Growth, Hematology, Tissue Morphology, GH/IGF Axis, and Antioxidant-Immune Responses in Nile Tilapia.
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Scientists found that fish exposed to both microplastics and mercury together—two pollutants increasingly common in waterways—suffered much worse health effects than fish exposed to either one alone, including organ damage, weaker immune function, and stunted growth. This matters because it shows how pollutants can team up to cause more harm than we'd expect from studying them separately, which raises questions about the combined effects of everyday contaminants on the seafood we eat and on our own bodies, since humans are also routinely exposed to both microplastics and trace mercury.
The single and combined effects of deltamethrin and polyethylene microplastics on the development and biochemical responses of Xenopus laevis in early life stages
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Researchers tested the single and combined effects of the pesticide deltamethrin and polyethylene microplastics on the African clawed frog during early development. While microplastics alone did not cause visible malformations or mortality, they altered biochemical enzyme activities and, when combined with the pesticide, produced complex interaction patterns including both additive and antagonistic effects. The study suggests that microplastic co-exposure can modify how aquatic organisms respond to pesticide toxicity.
Oxidative stress response biomarkers in gills and liver of bullfrog tadpoles semi-chronically exposed to combined microplastics and titanium dioxide nanoparticles
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Scientists exposed tadpoles to microplastics and titanium dioxide nanoparticles (common in sunscreens and food coloring) and found the combo caused more cell damage and stress than either pollutant alone, particularly harming liver function and energy metabolism. While this study was done in frogs, not humans, it's a warning sign: these same pollutants are widespread in our water and food, and we're typically exposed to them as mixtures, not one at a time—meaning their combined health effects on us may also be worse than tests on individual substances suggest.
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