My understanding is that it is a Defra initiative - but their hand is forced by complying with the EU Directive on Air Quality. States are supposed to set up a monitoring network and monitors are supposed to give a representative coverage of the area and also be positioned where the highest levels in a region may be experienced. Every five years or so the state is supposed to review its arrangements and see whether the pattern of coverage is appropriate.
Marylebone Road used to be considered the principal London hot spot - but after road transport vehicle PM10 emissions fell and it met EU standards, other stations, like Horn Lane, became the worst in London for particulates. Defra have eventually carried out their review and accordingly the Horn Lane location has now been included in the AURN which means that its results will be included in the UK annual summary which is reported to Europe. And whether Horn Lane meets the EU target becomes important for assessing whether the UK is meeting its air quality obligations. |