Why are nanoparticles potentially harmful for human health?

The tiny dimensions of nanoparticles (NPs) allow them to pass through the cell walls and, eventually, access the cell nucleus. The potential risks are cell toxicity, genotoxicity, and carcinogenicity. When they enter blood stream, they got translocated and accumulated in specific organs, particularly in those filtrating blood, where their presence can cause harmful effects. Some NPs can penetrate blood-brain barrier with still unknown consequences. They accumulate in food chain and affect environment.