Air quality compliance data

Under the Air Quality Standards Regulations 2010, the UK undertakes an air quality assessment and reports the findings on an annual basis. The assessment is based on a range of high-quality evidence including measurements from established monitoring networks and supplementary assessment in the form of air quality modelling. In 2020, Defra established the non-automatic UK Urban NO2 Network (UUNN) to complement the existing evidence base. The evidence is compared against Objective thresholds set for different pollutant/metric combinations associated for example with health effects and vegetation and ecosystem damage (see table below).

This page provides links to the following data resources, each associated with the compliance status and underlying evidence:

  • XML file library – a catalogue of download links for the machine-readable XML formats of the compliance data. The library is available below. For previous submissions, please see the European Environment Agency website.
  • Air Pollution in the UK annual report.
  • Spreadsheet of annual mean NO2 concentrations from the UK Urban NO2 Network.

Pollutants, metrics and legislative thresholds

The table below summarises the pollutant metrics in the UK’s Air Quality Standards Regulations (2010). These are the thresholds used to determine compliance and are referred to across the compliance app, compliance data hub, XML file library and in Air Pollution in the UK report.

Pollutant Averaging Period Objective Objective Type

NO2

Annual mean 40 µg m-3 Limit Value
NO2 Hourly mean 200 µg m-3, 18 permitted exceedances each year Limit Value
NOX Annual mean 30 µg m-3 Critical Level
SO2 Hourly mean 350 µg m-3, with 24 permitted exceedances each year Limit Value
SO2

24-hour mean

125 µg m-3, with 3 permitted exceedances each year

Limit Value

SO2

Annual mean

20 µg m-3

Critical Level

SO2

Winter mean

20 µg m-3

Critical Level

PM10

Annual mean

40 µg m-3

Limit Value

PM10 24-hour mean 50 µg m-3, with 35 permitted exceedances each year Limit Value
PM2.5 Annual mean 20 µg m-3 Limit Value (stage 2 – came into force 01/01/2020)
Benzene Annual mean 5 µg m-3 Limit Value

CO

maximum daily 8-hour mean

10 mg m-3

Limit Value

O3

maximum daily 8-hour mean

120 µg m-3, not to be exceeded on more than 25 days per calendar year averaged over three years

Target Value

O3

maximum daily 8-hour mean

120 µg m-3

Long Term Objective

O3

AOT40 (calculated from 1-hour values, May to July averaged over five years)

18000 μg m-3.h

Target Value

O3

AOT40 (calculated from 1-hour values, May to July)

6000 μg m-3.h

Long Term Objective

As

Annual mean

6 ng m-3

Target Value

Cd

Annual mean

5 ng m-3

Target Value

Ni

Annual mean

20 ng m-3

Target Value

Pb

Annual mean

0.5 µg m-3

Limit Value

benzo(a)pyrene (B(a)P)

Annual mean

1 ng m-3

Target Value