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Toxicity and behavioral responses of environmentally relevant microplastics in earthworms ( Eisenia fetida ): Ingestion, survival, reproduction, and avoidance across common polymer types
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Scientists tested how earthworms respond to microplastic pollution in soil, and found that even at high plastic levels, the worms didn't avoid contaminated soil, didn't get sick, reproduced normally, and barely absorbed the plastic particles into their bodies. This is good news for soil health and the food chain, since earthworms are key to healthy dirt and crops—but it doesn't mean microplastics are harmless overall, just that this particular worm species seems resilient to them under the tested conditions.
Microplastics (MPs) are recognized as ubiquitous contaminants in terrestrial ecosystems, yet their ecological risks to soil invertebrates remain poorly categorized, particularly at environmentally relevant exposure levels. This study investigated avoidance behaviour, ingestion, and toxicity of four common MP polymers (polyethylene; PE, polypropylene; PP, polyester/poly(ethylene terephthalate); PET, and polyacrylamide; PAM) in the earthworm Eisenia fetida using particle-based exposure concentrations. Standardized avoidance, reproduction, and ingestion assays were conducted across a wide concentration range (1,000-1,000,000 MP/kg dry soil) under controlled laboratory conditions. Avoidance responses were weak and highly variable across all polymers, with no consistent concentration-dependent patterns observed. Survival exceeded 90% in all treatments, and reproductive output showed no clear concentration-response relationship, with juvenile production at the highest exposure levels not differing from controls. MP ingestion was minimal at lower exposure concentrations, with sporadic detections occurring across polymers, but MPs across the polymers were detectable above similar threshold concentrations (∼80,800-92,800 MP/kg). Above these thresholds, ingestion increased predictably with log-transformed exposure concentration, showing comparable post-threshold ingestion patterns across polymers. Estimated bioaccumulation factors (BAFs), calculated at a standardized exposure concentration of 1,000,000 MP/kg, were low (0.0042-0.0124), indicating limited internal accumulation of MPs over the 28-day exposure period. Collectively, these results suggest that Eisenia fetida does not actively avoid MP-contaminated soils and does not retain MPs to a significant extent under the conditions tested. By integrating behavioural, ingestion, and toxicity endpoints and reporting exposure in particle-based units, this study provides ecologically relevant insights into MP-earthworm interactions and contributes to improving terrestrial MP risk assessment frameworks.
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Effects of Polyethylene Microplastics in Agricultural Soil on Eisenia fetida (Annelida: Oligochaeta) Behavior, Biomass, and Mortality
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Scientists tested how polyethylene microplastics in agricultural soil affected the behavior, body mass, and survival of the earthworm Eisenia fetida. Researchers found that earthworms actively avoided soil contaminated with microplastics and experienced changes in biomass at higher concentrations. The study suggests that microplastic pollution in farmland could negatively affect soil-dwelling organisms that play a key role in maintaining soil health.
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Researchers exposed earthworms to polyethylene microplastics of two sizes and found that smaller particles (13 micrometers) were more toxic than larger ones (130 micrometers), reducing survival and growth more severely. The microplastics caused oxidative stress in the worms and altered key soil properties including pH and organic carbon content. Since earthworms play a vital role in maintaining healthy soil for agriculture, this damage could affect soil quality and ultimately the food grown in microplastic-contaminated farmland.
Exposure to Microplastics Made of Plasmix-Based Materials at Low Amounts Did Not Induce Adverse Effects on the Earthworm Eisenia foetida
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Researchers exposed earthworms to low amounts of microplastics made from recycled mixed plastic waste and monitored their health over several weeks. They found no significant adverse effects on survival, growth, reproduction, or cellular damage at the concentrations tested. The study suggests that microplastics from this type of recycled material may pose limited risk to soil organisms at low environmental levels.
Responses of earthworms exposed to low-density polyethylene microplastic fragments
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Researchers exposed earthworms to low-density polyethylene microplastic fragments at various concentrations and studied the effects on their survival, growth, and reproduction. The microplastics affected earthworm behavior and caused measurable changes depending on concentration and exposure time. Since earthworms are critical for soil health and nutrient cycling, their sensitivity to microplastics raises concerns about how plastic pollution may degrade agricultural soils.
Defense responses in earthworms (Eisenia fetida) exposed to low-density polyethylene microplastics in soils
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Researchers exposed earthworms to low-density polyethylene microplastics in soil at various concentrations for 28 days. They found that the earthworms ingested microplastics in a dose-dependent manner and actually broke some particles into smaller pieces during digestion, with about 30% more particles under 100 micrometers found in their excrement compared to the original soil. At higher concentrations, the microplastics triggered oxidative stress and neurotoxic responses, suggesting potential ecological risks to soil organisms.
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