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Environmentally Persistent Free Radicals on Aged Polyamide Microplastics Drive Neurotoxicity in Eisenia fetida via a Glutamate-Centered Cascade
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Earthworms exposed to aged nylon (polyamide) microplastics in soil lost more body weight and showed higher signs of cell damage and nerve-related stress than those exposed to fresh microplastics. Lab analysis showed that chemical particles on the aged plastic triggered a chain of reactions involving brain chemicals and calcium, leading to nerve damage in the worms.
Abstract Nitrogen-containing microplastics (N-MPs) are widespread in soil and often exhibit distinct environmental behaviors and effects owing to their unique elemental composition and molecular structure. However, their toxicity to soil organisms remains poorly understood. To address this knowledge gap, the toxicity of pristine and aged polyamides (PA) was evaluated in earthworms (Eisenia fetida), a representative soil invertebrate. At 0.01% (w/w), aged PA increased the magnitude of body-weight loss, MDA levels, and AChE activity by 24.4%, 11.6%, and 24.1%, respectively, relative to pristine PA-MPs. Greater accumulation of aged PA-MPs was accompanied by enhanced oxidative damage and neurotoxicity. Integrated multiomics, quantitative real-time PCR, and biomarker analyses revealed that oxidative stress-mediated membrane damage promoted glutamate accumulation, receptor overactivation, Ca2+ overload, synaptic injury, and ultimately neurotoxicity. Pharmacological interventions and transmission electron microscopy of the ventral nerve cord provided functional and morphological support for this cascade. Radical quenching and comparative leachate bioassays further supported the important contribution of environmentally persistent free radicals in aged PA-MPs to neuronal damage. These findings define a mechanistic pathway for aged microplastic-induced neurotoxicity and provide a basis for assessing the ecological risks of aged N-MPs in soils.
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Environmentally relevant concentrations of microplastics from agricultural mulch and cadmium negatively impact earthworms by triggering neurotoxicity and disrupting homeostasis
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Researchers exposed earthworms to environmentally realistic levels of microplastics from agricultural mulch film combined with cadmium, a toxic heavy metal. The aged microplastics helped carry more cadmium into the earthworms' bodies, causing nerve damage, gut tissue injury, and disrupted metabolism. This study shows that microplastics in farm soil can make heavy metal contamination worse for soil organisms, with potential knock-on effects for the food chain.
Chronic exposure to UV-aged microplastics induces neurotoxicity by affecting dopamine, glutamate, and serotonin neurotransmission in Caenorhabditis elegans
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Researchers found that UV-aged microplastics caused more severe neurotoxic effects than pristine microplastics when worms were chronically exposed to low concentrations. The aged particles disrupted dopamine, glutamate, and serotonin signaling pathways and caused visible neurodegeneration in the test organisms. The study suggests that microplastics become more harmful as they weather in the environment, which is an important consideration for assessing real-world exposure risks.
Neurotoxicity induced by aged microplastics from plastic bowls: Abnormal neurotransmission in Caenorhabditis elegans
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Researchers found that microplastics released from aged plastic bowls caused nerve damage in the roundworm C. elegans at environmentally realistic concentrations. The aged microplastics disrupted neurotransmitter systems including dopamine and serotonin, leading to impaired movement. This study is concerning because it shows that everyday plastic items we use for food can release microplastics that have neurotoxic effects.
Understanding the harmful effects of polyethylene microplastics on Eisenia fetida: A toxicological evaluation
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Earthworms (Eisenia fetida) exposed to increasing concentrations of polyethylene microplastics in soil showed lower body weight, reduced reproductive output, and disrupted antioxidant defenses — with oxidative stress markers climbing nearly 1.3-fold at the highest dose. These findings confirm that microplastic pollution degrades soil ecosystem health at concentrations that could plausibly occur in contaminated agricultural land.
Photoaged microplastics induce neurotoxicity associated with damage to serotonergic, glutamatergic, dopaminergic, and GABAergic neuronal systems in Caenorhabditis elegans
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Researchers found that sunlight-aged microplastics caused more severe brain and nerve damage than fresh microplastics in lab worms, disrupting four major neurotransmitter systems: serotonin, glutamate, dopamine, and GABA. Even at very low, environmentally realistic concentrations, the aged particles impaired movement and altered gene expression related to nerve signaling. Since most microplastics in the real world have been weathered by sunlight, this study suggests that the neurotoxic risks of environmental microplastic exposure may be greater than studies using pristine particles indicate.
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