UntowardEffectsofMicro-andNanoplastics: AnExpertReviewofTheirBiologicalImpactand EpigeneticEffects

Abstract

The production of plastic has dramatically increased in the last 50 y. Because of their stability and durability, plastics are ubiquitously incorporated in both marine and terrestrial ecosystems. Plastic is acted upon by biological, chemical, and physical agents, leading to fragmentation into small pieces [i.e., microplastics (MPs) or nanoplastics (NPs)], classified depending on their size. MPs range from 0.1 to 5000 μm and NPs are fragments between0.001to0.1 μm.MPsand,especiallyNPs,areeasilyincorporatedintolivingbeingsviaingestion.ThepenetrationofMPsandNPsintothe food system is an important issue, for both food security and health risk assessment. Ingestion of different MPs and NPs has been associated with different issues in the intestine, such as direct physical damage, increased intestinal permeability, diminished microbiota diversity, and increases in local inflammatory response. However, the potential harmful effects of low-dose dietary plastic are still unclear. Some evidence indicates that intestinal uptake of plastic particles is relatively low and is mostly dependent on the particle’s size. However, other evidence highlights that NPs dysregulatekeymolecularsignalingpathways,modifythegutmicrobiotacomposition,andmayinduceimportantepigeneticchanges,including transgenerational effects that might be involved in the onset of many different metabolic disorders. Until now, experiments have been mostly performed on marine organisms, Caenorhabditiselegans, and mouse models, but some research indicates accidental plastic dietary consumption by humans, raising the issue of detrimental health effects of MPs and NPs. This review discusses the impact that MPs and NPs could have on the intestinal tract and the biodistribution and systemic, cellular, and molecular levels. Accumulated evidence of MPs’effects on the human gut suggeststhatlargeexposuretoMPsandNPsmayhavephenotypicaluntowardeffectsinhumans