Microplastics in bottled water and human health outcomes: a systematic review of multi-organ toxicity and mechanistic pathways.

This systematic review synthesized evidence on the health effects of microplastic exposure, with emphasis on organ-specific toxicity, molecular mechanisms, and implications for chronic disease. Following PRISMA 2020 guidelines, we searched PubMed, Scopus and Web of Science for peer-reviewed studies examining health outcomes associated with microplastic exposure relevant to bottled water consumption. Eligible studies included human observational studies, controlled animal experiments, and mechanistic in vitro investigations. Of 128 identified records, 15 studies met inclusion criteria: 3 human observational studies, 5 in vivo experiments, 4 in vitro investigations, and 3 mixed-design studies. Geographically, studies originated from China (40%), United States (20%), and other regions (40%). Polystyrene (10 studies), polyethylene, and polyethylene terephthalate (4 studies each) were most frequently investigated. Human biomonitoring confirmed microplastic presence in blood (3.15 ± 1.25 particles/mL), placental tissue (226-273 µg/g), and testicular samples (328 µg/g). Reproductive toxicity was the most consistently reported adverse outcome (5 studies), followed by hepatic, gastrointestinal, cardiovascular, renal, developmental, and neurological effects. Across studies, oxidative stress (reported in 12 studies), inflammatory activation (10 studies), endocrine disruption (4 studies), and mitochondrial dysfunction (4 studies) emerged as principal mechanistic pathways. Chronic exposure to microplastics from bottled water may contribute to multisystem toxicity through oxido-inflammatory mechanisms.