Micro- and nanoplastics, brain health, and One Health: a scoping review

Introduction: Micro- and nanoplastics (MNPs) are detectable in human brain tissue and cerebrospinal fluid, with concentrations elevated in individuals with dementia. Despite rapidly expanding evidence implicating MNPs in neuroinflammation, oxidative stress, blood–brain barrier (BBB) disruption, and neurotransmitter dysregulation, findings have not been systematically integrated across species. This systematic scoping review aims to map the extent, characteristics, and thematic patterns of existing evidence linking MNP exposure to brain-related outcomes, applying a One Health framework that integrates evidence from environmental, animal, and human neuroscience research to identify areas of mechanistic convergence and critical knowledge gaps. Materials and methods: A systematic scoping review was conducted across PubMed/MEDLINE, Web of Science, and Scopus in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Peer-reviewed studies reporting microplastic (MP < 5 mm) or nanoplastic (NP < 1 µm) exposure, including biodegradable polymers, with central nervous system outcomes were eligible. Screening and data extraction followed a standardised five-domain charting framework. Results: One hundred and eight studies (2016–2026) met inclusion criteria, spanning zebrafish (33), rodents (35 mice and 6 rats), seven human observational studies, and twenty-seven invertebrate, alternative teleost, and in vitro models. Polystyrene dominated the literature (64%). MNP exposure consistently elicited neuroinflammation through activation of nuclear factor kappa B (NF-κB) and the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, oxidative stress involving the reactive oxygen species (ROS)/superoxide dismutase 2 (SOD-2) axis, blood–brain barrier (BBB) impairment, and dopaminergic and cholinergic dysregulation. Conclusions: Convergent neurobiological responses across species support biological plausibility for MNP exposure as an emerging risk factor for human brain health. Methodological heterogeneity, polystyrene overrepresentation, and absent longitudinal human data constrain translational conclusions. A One Health framework is essential for directing future mechanistic and clinical research.