Emerging role of microplastics and nanoplastics in children's health.

Plastics are a growing environmental and health threat. Microplastics (MPs, <5 mm) and nanoplastics (NPs, <1 μm) are pervasive environmental contaminants increasingly detected within human tissues, including placenta, cord blood, breast milk, and infant stool, highlighting chronic early-life exposure. Children represent a uniquely vulnerable population due to higher intake relative to body mass, immature detoxification and immune systems, and rapid organogenesis. MPs and NPs (MNPs) can traverse biological barriers, accumulate in multiple organs, and disrupt key developmental processes through oxidative stress, inflammation, barrier dysfunction, and microbiome dysbiosis. Evidence from in vitro, animal and human studies indicates systemic impacts across gastrointestinal, pulmonary, endocrine, reproductive, immune, and central nervous systems, including impaired intestinal barrier function, dysbiosis, metabolic dysregulation, altered lung morphogenesis, endocrine disruption, reproductive abnormalities, immune dysregulation, and neurocognitive deficits. In addition, many chemicals associated with plastics pose risks to human health due to their toxicity and ability to leach into the surrounding area. This review compiles current knowledge on the physicochemical properties, exposure pathways, and system-specific effects of MNPs and the additives associated with plastics in pediatric populations. It also discusses the need for comprehensive policies to reduce plastic pollution. IMPACT: The increased prevalence of microplastics and nanoplastics pose a threat to children's health. Microplastics and nanoplastics have been found in many organs including the placenta. Children are particularly vulnerable to the effects of microplastics and nanoplastics. The mechanism by which they increase health risks in children are discussed.