Sorption to mulch film decreases bioavailability of two model pesticides for earthworms in soil

Antonia Seidel ¹, Isaac Heimbach ¹, Thomas-Benjamin Seiler ²

⁰Institute for Environmental Research, IFER, Aachen Biology and Biotechnology - ABBt, RWTH Aachen University, Aachen, Germany.

Ecotoxicology and Environmental Safety +

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November 10, 2025

View abstract on PubMed

Summary

Microplastics in agricultural soil can bind to pesticides, reducing their availability and toxicity to earthworms. This interaction may necessitate adjustments in farming practices to maintain pesticide effectiveness.

Area Of Science

Environmental Science
Agrochemistry
Ecotoxicology

Background

Microplastic pollution from mulch films is a growing concern in agricultural soils.
Microplastics interact with agrochemicals like pesticides, affecting their environmental fate and impact.
The combined effects of microplastics and pesticides on soil ecosystems are not well understood.

Purpose Of The Study

To investigate the interaction between polyethylene microplastics (MPP) and pesticides (Thiacloprid and Tebuconazole).
To determine the impact of MPP on pesticide extractability and toxicity to earthworms (Eisenia fetida).
To test the hypothesis that microplastics reduce pesticide bioavailability and toxicity.

Main Methods

Acute toxicity tests were performed on Eisenia fetida exposed to pesticides with and without MPP.
Pesticide extractability from soil was analyzed using CaCl2 and solvent extractions.
Commercial formulations of Thiacloprid (hydrophobic) and Tebuconazole (hydrophilic) were used.

Main Results

Microplastics slightly decreased pesticide toxicity, shifting the LC50 values for Tebuconazole and Thiacloprid.
Chemical analysis confirmed reduced pesticide availability in soil samples containing MPP.
MPP at application-relevant concentrations demonstrated a capacity to retain pesticides.

Conclusions

Polyethylene microplastics can retain pesticides in soil, thereby reducing their bioavailability and toxicity.
These findings have implications for pesticide efficacy in microplastic-contaminated soils.
Further research and mitigation strategies are needed to address the complex interactions between pesticides and microplastics in agricultural environments.

Keywords:

Biodegradable plastics Earthworm Microplastic Pesticide Soil Toxicity