S2144 GI Adverse Effects of Micro(nano) Plastic Exposure: A Systematic and Comprehensive Narrative Review

Introduction: Exposure to plastics is increasing at a logarithmic rate through countless products, including containers and packaging. Over time, discarded plastics degrade into micro (<5 μm) and nano (<1 μm) plastics (MNPs), which are released into water, soil, and air, ultimately reaching nearly all lifeforms. In humans, these particles are primarily ingested entering the gastrointestinal (GI) tract where they interact with gut microbiota, immune tissue, and mucosal barriers, contributing to inflammation and potential neoplastic impacts. A recent report noted a 50% increase in brain accumulation of MNPs from 2016 to 2024, highlighting increasing concerns. We evaluated current evidence on the potential impact of MNPs in GI disease. Methods: We conducted a comprehensive search of PubMed, EMBASE, and Cochrane databases from inception to February 2025. Studies evaluating the effects of MNPs on gut microbiota, GI inflammation and neoplasia were included. Results: Out of 800 screened studies, 15 met the eligibility criteria. Most studies examined MNP exposure through ingestion, particularly via contaminated water. Findings consistently reported gut dysbiosis, biofilm formation, increased antibiotic resistance, upregulation of cytokine/chemokines, and genotoxicity. High temperatures and repeated freeze/thaw cycles were shown to accelerate MNP release from plastic containers. MNPs demonstrated genotoxic potential and have been linked with hepatocellular and pancreatic cancers. Additionally, they interfere immune regulation by activating pattern recognition receptors and altering dendritic cell and regulatory T cell function. Animal models have linked MNP exposure to inflammatory bowel disease, liver cirrhosis, and metabolic-associated steatotic liver disease. Conclusion: There are numerous and diverse sources contributing to the ingestion of MNPs and associated GI risks. Although epidemiologic evidence is strongly suggestive, further research using environmentally relevant exposure levels is needed to better define risk. MNPs have demonstrated toxicity through multiple mechanisms, including inflammation, immune dysregulation, and carcinogenesis. These findings emphasize the urgent need for continued investigation, increased awareness among healthcare providers and patients, and development of strategies to reduce plastic exposures and related adverse health impacts.