Until recently engineering depended on a few widely available elements, today many products rely on a broad range of elements and materials.  These play a vital role in industrial sectors important to the UK such as automotive, aerospace and renewable energy technologies.  Our dependence on some is now so great that they are classified as critical and access to them is regarded as a strategic necessity. A material is classified as critical when it is of economic importance but is at risk of short supply.  These materials are not necessarily considered critical due to them being scarce, other factors are also considered:

• The economic importance associated with the products
• The risk associated with the supply of the material, for example due to political unrest in the producing countries
• Availability of viable substitutes, the materials possess unique properties

The EU, US and Japan have all taken steps to address the supply issues surrounding critical materials, elements and related technologies.  Each has defined their own list of critical materials depending on the expertise within that country/region and the importance that each material has on their key industrial sectors.

• The EU carries out a criticality assessment every three years; in July 2017 the EU published a revised methodology for the assessment and a forth list of critical materials was published in 2020 containing 30 materials.
• A federal strategy to ensure secure and reliable supplies of critical minerals was issued in December 2017 by the US directing federal agencies to develop a list of critical minerals, strategies to reduce reliance on critical minerals and action to support increase domestic supply of critical minerals. In May 2018 a list containing 35 minerals considered critical to the economic and national security of the US was published.