The protective layer formed by soil particles on plastics decreases the toxicity of polystyrene microplastics to earthworms (Eisenia fetida)

•Aging in soil lead the surface of PS-MP being wrapped by soil particles.•The wrapping effects of soil particles induced the formation of protective layer.•Protective layer increased the particle size of PS-MP and decreased its ingestion.•The aging of PS-MP in the soil decreased its toxicity to earthworms.