From 2016 - https://science.sciencemag.org/content/351/6277/1039.1.full seems to point to a paywall link https://pubs.acs.org/doi/full/10.1021/acs.est.5b05478

> They show that environmentally relevant microplastic concentrations led to reduced earthworm growth and elevated mortality as compared to a control. Futhermore, earthworms may transport microplastics into soils, from which they may leach into surface waters.