Impact of microplastics on the human gut microbiome: a systematic review of microbial composition, diversity, and metabolic disruptions.

Global plastic waste production remains a critical environmental issue. Microplastics (MPs), plastic particles less than 5 mm, are now pervasive across ecosystems. Humans are exposed to MPs via ingestion, inhalation, and dermal contact raising concerns about their health impacts. This systematic review investigates the influence of MPs on the human gut microbiome, focusing on changes in microbial composition, diversity, and metabolic pathways based on 12 studies identified through Scopus and PubMed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Findings show that exposure to MPs such as polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polylactic acid (PLA), induces gut dysbiosis, marked by a loss of beneficial genera, and enrichment of pathogenic species. MPs also impair short-chain fatty acid (SCFA) production, alter metabolic functions, and modulate immune pathways, contributing to intestinal diseases, metabolic syndrome, and chronic inflammation. The extent of disruption is influenced by MP-specific properties such as type, size, and concentration. These results suggest that MPs are emerging environmental risk factors with tangible implications for human health. To fully understand the health concerns associated with MPs long-term, human-relevant studies with standardized methodologies are urgently needed to define safe exposure levels and guide policies aimed at reducing MP-related health risks.