The 2008 Ambient Air Quality Directive (2008/50/EC) sets legally binding limits and target values for concentrations of major air pollutants. It merges and replaces nearly all the previous EU air quality legislation and incorporates the 4th daughter directive. It was transposed into law across the UK through the Air Quality Standards Regulations 2010.
Generally this directive protects human health. It sets limit values for lead (Pb), nitrogen dioxide (NO2), particulate matter (PM10 and PM2.5), sulphur dioxide (SO2), benzene, carbon monoxide (CO), certain toxic heavy metals (arsenic, cadmium, nickel and benzo(a)pyrene) and polycyclic aromatic hydrocarbons (PaH) and ozone (O3). There is a target value and a long-term objective for ozone is intended to provide protection for vegetation.
There are also limit values for nitrogen dioxide and sulphur dioxide to protect vegetation but these do not need to be applied near major roads, built up areas or industrial processes, so in practice in the UK they provide little protection for ecosystems. However the industrial regulatory bodies have agreed with the countryside agencies that they will use these as standards against which to judge harm for sensitive wildlife sites.
Member States are required to produce air quality plans for zones where target or limit values are exceeded and must take all necessary measures (not entailing disproportionate costs for target values and long-term objectives) to ensure limits are attained.
A number of member states (including the UK) have experienced difficulties in meeting some of the limit values set out in the directive. The directive includes the option of applying for time extensions from limit values in zones where limits are being exceeded, provided plans and appropriate measures are put in place to ensure compliance within the shortest possible time. The UK was successful in applying for a time extension (to 11 June 2011) for PM10 in all the zones it applied for. For NO2, the UK was successful in requesting time extensions (to 1 January 2015) for 9 zones, 15 zones were rejected and exceedances in 19 zones weren’t applied for as it was deemed that compliance woul dnot be achieved within the time extension. These time extensions have now ceased.
A small number of zones in the UK still exceed some target values (e.g. nickel, PAH) and the long-term ozone objective to protect vegetation is exceeded in the majority of zones. The nitrogen dioxide limit value is exceeded in a number of zones. The government published an action plan to address compliance in December 2015.