Harmful Effects of Microplastics and Nanoplastics in Human Body Systems: A Systematic Review

Background: Microplastics and nanoplastics (MNPs) are ubiquitous environmental contaminants from plastic degradation, leading to human exposure through ingestion, inhalation, and dermal contact. While emerging evidence suggests potential health effects, comprehensive human-specific data remain limited. Objective: To systematically review evidence on MNP exposure and health impacts across human organ systems. Methods: Following PRISMA guidelines, we searched Embase, Environment Complete, MEDLINE, and Scopus for peer-reviewed English-language studies published between 2020 and 2025 that reported MNP exposure in adult human populations and addressed at least one organ system. Thirty studies met inclusion criteria, and all clinical studies were assessed for risk of bias using the Newcastle–Ottawa Scale (NOS) Results: Clinical studies consistently detected MNPs in human blood, thrombi, feces, and respiratory and reproductive tissues. Higher MNP burdens correlated with increased disease severity across cardiovascular, gastrointestinal, respiratory, musculoskeletal, and reproductive systems. In vitro studies using human-derived cell lines demonstrated that MNPs penetrate cells and disrupt cellular processes, inducing oxidative stress, cytotoxicity, mitochondrial dysfunction, inflammation, DNA damage, and apoptosis. Toxic effects were size-, polymer-, and concentration-dependent, with smaller particles exhibiting greater cellular uptake and toxicity. Conclusions: Human MNP exposure is widespread and associated with adverse biological effects across multiple organ systems. Further interdisciplinary research is needed to establish causal relationships and inform risk assessment and regulatory frameworks for plastic-associated contaminants. Other: This research received no external funding. The research protocol was registered with PROSPERO (Registration ID number CRD420261284559).