Systemic Accumulation and Distribution of Micro- and Nanoplastics in Human Tissues and Their Impact on Health: A Systematic Review

This project is a systematic review aimed at synthesising human evidence on the presence, systemic distribution, and potential health implications of microplastics (MPs) and nanoplastics (NPs) in human tissues and biological fluids. Micro- and nanoplastics have emerged as pervasive environmental contaminants with increasing evidence of internal human exposure. Recent studies have reported the detection of plastic particles in clinically relevant matrices including blood, lung tissue, placenta, breast milk, liver, semen, cerebrospinal fluid, urine, and vascular tissues. These findings suggest that MPs and NPs are capable of crossing biological barriers and reaching multiple organ systems. However, the human evidence base is fragmented, methodologically heterogeneous, and difficult to interpret in terms of biological relevance and public health impact. The purpose of this review is to systematically collect, appraise, and synthesise primary human studies published between 2020 and 2025 that investigate the detection, accumulation, systemic distribution, and biologically relevant effects of micro- and nanoplastics in human tissues and fluids. The review also aims to evaluate methodological quality, contamination control practices, and analytical approaches used in human biomonitoring studies. Particular attention is given to vulnerable life stages (maternal–fetal exposure, early life, ageing) and to organ systems potentially affected by chronic low-grade inflammatory and oxidative stress mechanisms. This review follows PRISMA 2020 guidelines. PubMed and Scopus are searched using predefined strategies. Eligibility criteria are restricted to peer-reviewed human studies involving direct detection or quantification of MPs/NPs in clinical, surgical, or post-mortem specimens. Data extraction includes study design, biological matrix, analytical techniques, polymer characteristics, and reported biological or clinical outcomes. Risk of bias is assessed in primary human studies using design-appropriate tools (Newcastle–Ottawa Scale and QUADAS-2). Because of expected heterogeneity in analytical pipelines and reporting metrics, a qualitative synthesis is planned rather than a meta-analysis. The expected outcome of this project is a structured evidence map of human internal exposure to micro- and nanoplastics, identification of methodological gaps, and a conceptual framework linking detection evidence with potential public health implications across the life course. The results are intended to inform future biomonitoring research, standardisation of analytical protocols, and risk assessment strategies within a One Health and public health perspective.