Abstract

Microplastics and nanoplastics now contaminate every human compartment examined, including blood, placenta, atheromatous plaque, and brain tissue. The brain warrants particular attention. Decedent brain tissue has been shown to carry microplastic concentrations seven to thirty times higher than liver or kidney, with a 50% rise documented between 2016 and 2024, and the highest burdens observed in donors with diagnosed dementia. Animal data confirm that nanoscale particles cross the blood-brain barrier within hours of oral exposure. Ultra-processed foods, which now account for more than half of caloric intake in the United States, serve as high-throughput delivery vehicles for microplastics via packaging migration, mechanical processing, and contamination. They have themselves been independently linked in large prospective cohorts to depression, anxiety, cognitive decline, stroke, and dementia. The convergence of high tissue burden, biologically plausible mechanism, and a population-scale modifiable exposure vehicle defines a Brain Health emergency. We outline what is known, what is not yet measurable, and where the field must move next, with attention to vulnerable populations including pregnant women, children, and patients with established neurological or cardiovascular disease.