Nanoparticles can have the same dimensions as some biological molecules and can interact with these. In humans and in other living organisms, they may move inside the body, reach the blood and organs such as the liver or the heart, and may also cross cell membranes. Insoluble nanoparticles are a greater health concern because they can persist in the body for long periods of time.
Nanotechnology, now used in everything from computers to toothpaste, is booming. But concern is growing that its development is outpacing our understanding of how to use it safely.