Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 to 1000 nanometres (10−9 meter) but usually is 1 to 100 nm (the usual definition of nanoscale).
Metals released into the atmosphere from human activities pose a significant risk to ecosystems and human health. Small airborne particles with a diameter of less than 10 microns can be inhaled and then absorbed into the alveolar tissue of the lungs, resulting in damage.