The Committee on the Medical Effects of Air Pollutants (COMEAP) was asked by Defra and the Devolved Administrations to review the Air Quality Index to ensure that it is fit for purpose given developments in the field of air quality. The current index has been in operation essentially unchanged for a period of around 12 years. COMEAP published the report Review of the UK Air Quality Index in June 2011. Defra and the Devolved Administrations have considered the report recommendations and will implement several changes, following consultation with index users. The implementation of the new index, to be renamed the Daily Air Quality Index (DAQI) is described in this letter.