The decision to revoke an Air Quality Management Area (AQMA) should only be taken following a Detailed Assessment or Further Assessment. This should set out in detail all the available information used to reach the decision. In some instances if compelling evidence exists, an AQMA can be revoked following an Updating and Screening Assessment or Progress Report.
Pollutant concentrations may vary significantly from one year to the next, due to the influence of meteorological conditions, and it is important that authorities avoid cycling between declaring, revoking and declaring again, due to these variations. Before revoking an AQMA on the basis of measured pollutant concentrations, the authority therefore needs to be reasonably certain that any future exceedences (that might occur in more adverse meteorological conditions) are unlikely. For this reason, it is expected that authorities will need to consider measurements carried out over several years or more, national trends in emissions, as well as local factors that may affect the AQMA, including measures introduced as part of the Action Plan, together with information from national monitoring on high and low pollution years.
As a hypothetical example, an AQMA was declared in 2005 on the basis of modelling predictions, which indicated a maximum annual mean nitrogen dioxide concentration in 2016 of 43 µg/m3 . Monitoring commenced at a worst-case relevant exposure location in 2017, for which an annual mean of 41µg/m3 was measured. Concentrations declined in 2018 to 38 µg/m3, but no decision was taken at this stage to revoke the AQMA due to the uncertainty in future year concentrations. Further monitoring in 2019 and 2020 confirms annual mean concentrations below the objective. The AQMA would then be formally revoked in 2020 following a Detailed Assessment that confirmed a significant downward trend in concentrations.
Just as in declaring an AQMA, local authorities will need to revoke their AQMAs officially by means of an AQMA Revocation Order. Defra or the relevant Devolved Administration should be informed once this has happened.
Below is an example of an AQMA Revocation Order.
Released: November 2009 (PDF, 500 KB, 2 pages)