1. What are nanomaterials?
Nanomaterials are distinguished mainly by size. As in the expanding area of nanotechnology, the prefix "nano” denotes something with specific structure at the nanoscale. This is most commonly taken as being 100 nanometres (100 millionths of a millimetre or 100 billionths of a metre) or less. It extends down to 1 nm.
Nanotechnology covers devices or systems made by manipulating individual atoms or molecules. It also denotes anything which contains very small structures or particles, which can be produced by machining or processing.
There are many types of nanomaterials. They may be produced by "top-down” processing of bulk materials, by milling for example. Or they may result from "bottom-up” methods such as chemical synthesis, or by self-assembly from carefully prepared smaller components. All these methods may be used in combination, in carefully designed sequences.
A particular nanomaterial may also have one element or lots of different ones. It may be simple or complex, organic or inorganic, and may be physically or chemically modified. Nanomaterials may have multiple components, occur in aggregates or composites, and have varied internal structure.
All these features may affect nanomaterials’ properties. Their small size and surface properties, including large surface areas, mean that the way they interact, chemically or physically, may differ from larger scale materials. This is not inherently hazardous, but nevertheless poses novel challenges for risk assessment of such materials as they enter wider use. Such risk assessments need to be underpinned by a working definition of nanomaterials. This would guide regulators in deciding which products may need a specific examination which differs from established testing procedures.