What Are Nanoplastics?

The FDA says microplastics are typically considered smaller than five millimeters in at least one dimension, and nanoplastics are even smaller, typically less than one micron, while noting there are currently no standard size definitions. For scale, it says a human hair is about 70 microns wide.

New tools are finding far more of them. NIH reports that a Columbia University team led by Drs. Wei Min and Beizhan Yan developed a microscopy approach to detect individual micro- and nanoplastic particles, and that when they analyzed three popular brands of bottled water, results published in January 2024 found about 240,000 tiny pieces of plastic per liter on average, about 90 percent of them nanoplastics. An NIEHS-funded study published in Nature Medicine in 2025 reported that plastic concentrations in postmortem liver and brain samples tended to rise from 2016 to 2024, that brain tissue held more plastic than liver or kidney, and that more was found in the brains of people with a dementia diagnosis, while the authors said more research is needed on whether these exposures contribute to health effects.

The health question is open. The FDA says microplastics and nanoplastics have been found in human urine, stool, blood and organs, but not enough is known about their potential health effects, and that current scientific evidence does not demonstrate that the levels detected in foods pose a risk to human health.