Air quality expert group - Fine particulate matter (PM2.5) in ... - Defra

PM2.5 in the UK
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3.8 PM2.5 concentrations in relation to standards
3.8.1 EU and UK requirements for PM2.5
31. The EU limit values and targets for PM2.5 set out in the Ambient Air Quality
Directive (2008/50/EC) are all based on annual mean concentrations (see Table
1.1 in Chapter 1). The limit value is 25 µg m -3 as an annual mean and it is to be
met by 2015. This limit value is seen as a long-stop and is not designed to drive
policy. All the evidence indicates that this concentration will not be exceeded in
the UK. The highest annual mean roadside concentration in 2009 was 21 µg m -3
at the Marylebone Road kerbside site in London (84% data capture). In 2010
the highest concentration was at Glasgow kerbside at 23.1 µg m -3 (96% data
capture). Although these values are below the 25 µg m -3 limit value for 2015, they
are above the Stage 2 indicative limit value of 20 µg m -3 to be achieved by 2020.
32. The EU Directive exposure reduction target and exposure concentration
obligation are based on the average exposure indicator (AEI). The AEI is an
exposure index calculated as the average across a designated set of UK urban
background sites. The indicative AEI for these sites in 2009 was 12.3 µg m -3 and
in 2010 13.0 µg m -3 (these calculations were made for sites with > 75% data
capture and include data collected with both FDMS and Partisol instruments).
These values are very close to the boundary between a requirement for a 10%
or 15% exposure reduction target. It is thus unclear at this stage what the EU
target reduction for the UK will be as the AEI is based on the three-year mean
(2011 results will thus be crucial in determining the AEI). A 10% target would
require a reduction of around 1.3 µg m -3 , while a 15% target would require a
reduction of around 2 µg m -3 , which will be more challenging.
33. Finally, there is the exposure concentration obligation (ECO) within the Directive,
which sets a ceiling of 20 µg m -3 for the AEI, to be achieved by 2015 as a threeyear
mean for the same set of urban background sites used to determine the
exposure reduction target. Given that the AEI is likely to be around 13 µg m -3 ,
this obligation will not be exceeded.
34. The UK Government has set an annual mean objective for PM2.5 of 25 µg m -3 ,
which applies at all relevant exposure locations in England, Wales and Northern
Ireland from 2020. 4 Given the discussion above, this is likely to be achieved
throughout the UK. The UK Air Quality Strategy has also set an exposure
reduction objective, which in this case is a 15% reduction between 2010 and
2020. This will either be the same as, or possibly more stringent than the EU
target, which will be either 10% or 15%.
35. In Scotland the annual mean objective for PM2.5 has been set at 12 µg m -3 to be
achieved by 2020 at all relevant exposure locations. Given that the measured
kerbside concentration in Glasgow was 23 µg m -3 in 2010, it is highly likely that
the objective is currently being exceeded at roadside sites in major urban areas
in Scotland. There is thus a risk that the Scottish objective for PM2.5 may still be
exceeded in 2020.
4 This was set before the EU limit value was set. The latter is the same concentration, but applies from 2015, and will effectively supersede
the UK objective.