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The accumulation of microplastics poses potential risks to soil health. Here, we did a preliminary exploration on the potential of Lumbricus terrestris (Oligochaeta) to reduce low-density polyethylene (LDPE), polylactic acid (PLA), and polybutylene adipate terephthalate (PBAT) microplastic (20–648 µm) contamination in soils. The ingestion of microplastics-contaminated soil (1% of microplastics, dw/dw) in a mesocosm system and the ingestion of pure microplastics in the Petri Dish by earthworms were studied. Results show that earthworms survived in the microplastics-contaminated soil (0% mortality in 35 days) but barely when exposed solely to microplastics (30–80% mortality in 4 days). Size-dependent ingestion of microplastics was not observed. The fragmentation of LDPE microplastics in the gizzard facilitated by soil was confirmed by the significantly increased ratio of small-sized (20–113 µm) microplastics from the bulk soil to the gut (from 8.4% to 18.8%). PLA and PBAT microplastics were fragmented by gizzard without the facilitation of soil, the ratios of small-sized (20–113 µm) PLA and PBAT microplastics in the gut were 55.5% and 108.2% higher than in respective pristine distributions. Substantial depolymerization of PLA (weight-average molar mass reduced by 17.7% with shift in molecular weight distribution) and suspected depolymerization of PBAT were observed in the worm gut, while no change in the molar mass was observed for PLA and PBAT microplastics buried in the soil for 49 days. Our results suggest that ingested microplastics could undergo fragmentation and depolymerization (for certain polymers) in the earthworm gut. Further research is needed to reveal the mechanisms of polymer depolymerization in the earthworm gut and to evaluate the feasibility of microplastic bioremediation with earthworms.

Although (micro)plastic contamination is a worldwide concern, most scientific literature only restates that issue rather than presenting strategies to cope with it. This critical review assembles the current knowledge on policies and responses to tackle plastic pollution, including peer-reviewed scientific literature, gray literature and relevant reports to provide: (1) a timeline of policies directly or indirectly addressing microplastics; (2) the most up-to-date upstream responses to prevent microplastics pollution, such as circular economy, behavioral change, development of bio-based polymers and market-based instruments as well as source-specific strategies, focusing on the clothing industry, tire and road wear particles, antifouling paints and recreational activities; (3) a set of downstream responses tackling microplastics, such as waste to energy, degradation, water treatment plants and litter clean-up strategies; and examples of (4) multifaceted responses focused on both mitigating and preventing microplastics pollution, e.g., approaches implemented in fisheries and aquaculture facilities. Preventive strategies and multifaceted responses are postulated as pivotal to handling the exacerbated release of microplastics in the environment, while downstream responses stand out as auxiliary strategies to the chief upstream responses. The information gathered here bridges the knowledge gaps on (micro)plastic pollution by providing a synthesized baseline material for further studies addressing this environmental issue.