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<p>Between 1997 and 2000 inclusive, the limit value for hourly mean concentrations
of nitrogen dioxide was 200 µg/m<sup>3</sup> and could only be exceeded for two percent
of the calendar year for any monitoring site. This limit was determined by the Council
Directive on air quality standards for nitrogen dioxide (85/203/EEC). All air quality
monitoring sites for nitrogen dioxide were compliant with the limit value between
1997 and 2000.</p><p> </p><p>Under the First Daughter Directive (1999/30/EC) and Air
Quality Directive (2008/50/EC), the limit value for hourly mean nitrogen dioxide concentrations
is 200 µg/m<sup>3</sup> and Member States are allowed to exceed this limit for a maximum
of 18 hours per calendar year. The monitoring sites with the greatest number of hours
in exceedance of this limit by year are displayed in the table below (site measurements
are available on the UK-AIR website):</p><p> </p><p> </p><table><tbody><tr><td><p><strong>Year</strong></p></td><td><p><strong>Assessment
area</strong></p></td><td><p><strong>Monitoring site</strong></p></td><td><p><strong>Hours
with NO<sub>2</sub> concentration > 200 µgm<sup>-3</sup></strong></p></td></tr><tr><td><p>2001</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>60</p></td></tr><tr><td><p>2002</p></td><td><p>Glasgow
Urban Area</p></td><td><p>Glasgow Kerbside</p></td><td><p>38</p></td></tr><tr><td><p>2003</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>471</p></td></tr><tr><td><p>2004</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>542</p></td></tr><tr><td><p>2005</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>853</p></td></tr><tr><td><p>2006</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>686</p></td></tr><tr><td><p>2007</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>458</p></td></tr><tr><td><p>2008</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>822</p></td></tr><tr><td><p>2009</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>486</p></td></tr><tr><td><p>2010</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>539</p></td></tr><tr><td><p>2011</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>229</p></td></tr><tr><td><p>2012</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>132</p></td></tr><tr><td><p>2013</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>60</p></td></tr><tr><td><p>2014</p></td><td><p>Greater
London Urban Area</p></td><td><p>London Marylebone Road</p></td><td><p>60</p></td></tr><tr><td><p>2015</p></td><td><p>South
Wales</p></td><td><p>Hafod-yr-ynys Roadside</p></td><td><p>108</p></td></tr><tr><td><p>2016</p></td><td><p>South
Wales</p></td><td><p>Hafod-yr-ynys Roadside</p></td><td><p>126</p></td></tr></tbody></table><p>
</p><p> </p><p>The limit value for annual mean nitrogen dioxide concentrations is
40 µg/m<sup>3</sup>. Assessment is made using a mixture of monitoring site data, modelling
of major roadside concentrations in urban areas and modelling of background concentrations.
The maximum annual mean concentration of nitrogen dioxide and its location in the
UK are displayed in the table below (monitoring and modelling data can be found on
the UK-AIR website):</p><p> </p><table><tbody><tr><td><p><strong>Year</strong></p></td><td><p><strong>Assessment
area</strong></p></td><td><p><strong>Location</strong></p></td><td><p><strong>Annual
mean NO<sub>2</sub> concentration (µg/m<sup>3</sup>)</strong></p></td></tr><tr><td><p>2001</p></td><td><p>Central
Scotland</p></td><td><p>Modelled background location east of Glasgow (close to A73
and B803)</p></td><td><p>95</p></td></tr><tr><td><p>2002</p></td><td><p>Greater London
Urban Area</p></td><td><p>A3211 (between City of London boundary and A201 Blackfriars
Bridge junction)</p></td><td><p>87</p></td></tr><tr><td><p>2003</p></td><td><p>Greater
London Urban Area</p></td><td><p>A501 (between Marylebone High St and A4201 junctions)</p></td><td><p>109</p></td></tr><tr><td><p>2004</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Portman St and Duke St junctions)</p></td><td><p>113</p></td></tr><tr><td><p>2005</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Portman St and Duke St junctions)</p></td><td><p>184</p></td></tr><tr><td><p>2006</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Portman St and Duke St junctions)</p></td><td><p>168</p></td></tr><tr><td><p>2007</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Marble Arch and Portman St junctions)</p></td><td><p>155</p></td></tr><tr><td><p>2008</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Marble Arch and Portman St junctions)</p></td><td><p>182</p></td></tr><tr><td><p>2009</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Portman St and Duke St junctions)</p></td><td><p>163</p></td></tr><tr><td><p>2010</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Portman St and Duke St junctions)</p></td><td><p>170</p></td></tr><tr><td><p>2011</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between Portman St and Duke St junctions)</p></td><td><p>136</p></td></tr><tr><td><p>2012</p></td><td><p>Greater
London Urban Area</p></td><td><p>A302 (between A3217 and A4 junctions)</p></td><td><p>152</p></td></tr><tr><td><p>2013</p></td><td><p>Greater
London Urban Area</p></td><td><p>A4 (between A315/A3216 and Hyde Park Corner junctions)</p></td><td><p>126</p></td></tr><tr><td><p>2014</p></td><td><p>Greater
London Urban Area</p></td><td><p>A40 (between A4206 and A5/A501 junctions)</p></td><td><p>119</p></td></tr><tr><td><p>2015</p></td><td><p>Greater
London Urban Area</p></td><td><p>A3211 (between A100 junction and Tower Hamlets boundary)</p></td><td><p>115</p></td></tr><tr><td><p>2016</p></td><td><p>Greater
London Urban Area</p></td><td><p>A3211 (between Arthur St and Fish St Hill junctions)</p></td><td><p>102</p></td></tr></tbody></table><p>
</p><p>The UK is compliant with the Air Quality Directive and its predecessors regarding
concentrations of PM<sub>2.5</sub>. All areas of the UK had maximum annual mean concentrations
less than 20 µg/m<sup>3</sup> in 2016 (the limit value set by the European Union);
but in every year some areas across the UK have exceed the WHO guideline of 10 µg/m<sup>3</sup>
annual mean and a 24-hour mean of 25 µg/m<sup>3</sup>. Weighting the concentrations
according to where the population lives gives annual mean concentrations which are
less than the WHO guideline (9 µg/m<sup>3</sup> in 2016).</p><p> </p>
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