The impact of microplastics on global public health, distribution, and contamination: a systematic review and meta-analysis

Microplastics (MPs), defined as plastic particles smaller than 5 mm, are an emerging environmental contaminant of concern due to their widespread presence in air, water, food, and human tissue. Although the evidence has identified MPs in the bloodstream, placentas, and excrement, suggesting chronic internal exposure, MPs' health outcomes and biological mechanisms remain inadequate. This systematic review and meta-analysis follow PRISMA 2020 guidelines, and the Coherence risk of bias tools to evaluate MPs' exposure pathways and health risks. A comprehensive search across PubMed, Scopus, Web of Science, Embase, Cochrane, and other databases identified 2441 initial records. 78 studies met the inclusion criteria. Ingestion, inhalation, and dermal contact pathways were analysed, and observational and toxicological studies were assessed. Ingestion accounted for ~ 74% of MP exposure pathways, followed by inhalation (22%) and dermal absorption (4%). MPs were detected in 33–65% of human faecal and blood samples across national surveys. Meta-analysis-random-effects models and test of overall effect size z = 1.18, p-value = 0,24 were used to account for inter-study variance. Homogeneity: Q  = 1.16 and Heterogeneity: H-squared = 1,00. Animal studies suggest MPs induce oxidative stress, inflammation, immune disruption, and endocrine effects. However, causality in human populations remains unverified due to inconsistent study designs and exposure quantification methods. Subgroup analysis revealed stronger associations with reproductive, gastrointestinal, and neurotoxic markers in rodent models. MPs exposure is recognised as a ubiquitous and potentially hazardous public health concern. This study underscores the pressing need for long-term studies and effective public risk strategies to mitigate human exposure and safeguard the ecosystem.