Distribution and health impacts of micro- and nanoplastics (MNPs) in human organs: Accumulation, translocation, and toxicity – A systematic review of current evidence

This review synthesizes current evidence on the presence, accumulation, and toxicity of micro- and nanoplastics (MNPs) in the human body, highlighting mechanistic pathways of contamination and related health risks. This systematic analysis of peer-reviewed literature reveals MNPs presence in human stool (1–36 particles/g), blood (1.84–4.65 µg/mL), lungs (14.19 ± 14.57 particles/g), placenta (0.28–9.55 particles/g), and arterial plaques (up to 118.66 ± 53.87 µg/g), with polyethylene (PE), polystyrene (PS), and polypropylene (PP) as the most common polymers. Annual ingestion estimates suggest adults may consume ∼50,000 particles and children ∼8000 particles, primarily from bottled water, salt, and seafood. Lifetime accumulation within tissues, however, has been estimated separately, suggesting long-term buildup across organs. Bottle-fed infants may ingest up to ∼1.5 million MPs annually from formula prepared in polypropylene bottles. This distinction clarifies that annual ingestion values represent intake through diet and water, whereas lifetime estimates reflect modeled accumulation within body tissues. Among exposure routes, ingestion represents the most significant pathway, with inhalation contributing secondarily, while dermal absorption appears minimal. Notably, females showed significantly higher GI tract microplastic accumulation than males, and 58.4 % of carotid plaques from atherosclerotic patients contained MNPs, indicating potential cardiovascular implications. MNPs ≤ 1 µm were consistently associated with oxidative stress, DNA damage, and increased cytotoxicity, especially at concentrations ≥ 200 μg/mL. This review underscores the critical necessity for standardized exposure models and human-relevant dose assessments to understand the toxic consequences of MNPs better and guide future public health and regulatory strategies. • MPs found in stool (1–36/g), blood (1.84–4.65 µg/mL), lungs (14.19 ± 14.57/g). • Placenta (0.28–9.55/g) and plaques (up to 118.66 ± 53.87 µg/g) contain MPs. • Adults ingest over 25,000 MPs/year; infants up to 1.5 million from bottle-feeding. • PE, PS, and PP dominate as the top three polymers found in human samples. • MPs ≤ 1 µm linked to oxidative stress, DNA damage, and cytotoxicity ≥ 200 μg/mL.