A1: Emissions for five key air pollutants
Short Description
This indicator shows changes in the emissions of the 5 key air pollutants: fine particulate matter (PM2.5), nitrogen oxides (NOx), ammonia (NH3), non-methane volatile compounds (NMVOCs) and sulphur dioxide (SO2).
Air pollution has negative impacts on human health and the environment. Long-term exposure to particulate matter contributes to the risk of developing cardiovascular diseases and lung cancer. As well as being emitted directly, particulate matter can be formed in the atmosphere from reactions between other pollutants, of which SO2, NOx, NMVOCs and NH3 are the most important. NOx and NH3 emissions can be deposited in soils or in rivers and lakes, for example, through rain. Resulting nutrient nitrogen deposition affects nutrient levels and species diversity in sensitive environments, for example, by encouraging algae growth in lakes and water courses. Chemical reactions between NOx and NMVOCs produce ozone (O3), which damages human health and crops. O3 damages habitats, which impacts on wildlife, and ozone can react with other chemicals in the air to form smog.
This indicator provides an assessment of pressures on the atmosphere caused by the emissions of the 5 key air pollutants, which, when concentrated in the air or later deposited into soil or water, have impacts on human health and ecosystems.
Readiness and links to data
Emissions data are published annually in the Air Quality Pollutant Inventories 2005-2021. These data may differ from the data appearing in this indicator because of differences in the timing of annual updates and because the entire time series is revised when new data points are added.
Notes on indicator
Consultation with the devolved administrations led to an agreement to limit updates to historic devolved administration air pollutant inventories to 2005 as this is the base year for legally binding emissions reductions commitments. This also allows more resource to be allocated to the development of more recent years of the time series for which there is better access to updated methods and data. A UK-wide historic time series of emissions for each of the air pollutants included within this indicator remains available back to 1970. These data are published each February as part of Defra’s annual reporting on the Emissions of air pollutants.
It is not possible to measure precisely how much of each pollutant is emitted into the atmosphere by every source. Therefore, modelling is used to estimate the level of activity of each source and the emissions released from each type of source. All modelling has an associated level of uncertainty, and each pollutant included within this indicator has a different level of uncertainty depending on the underlying data and assumptions that contribute to the calculations. More information can be found in the 'Methods and quality processes for UK air pollutant emissions statistics' document published alongside the National Statistics on the Emissions of air pollutants in the UK.
Indicator components
Figure A1: Emissions for five key air pollutants in England, 2005 to 2021
Table A1: Emissions for five key air pollutants in England, 2005 to 2021
| Year | NH3 | NMVOCs | NOx | PM2.5 | SO2 |
|---|---|---|---|---|---|
| 2005 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 |
| 2006 | 99.62 | 94.92 | 96.11 | 98.52 | 91.15 |
| 2007 | 97.90 | 90.69 | 92.97 | 90.66 | 81.24 |
| 2008 | 91.90 | 82.98 | 81.47 | 84.53 | 67.75 |
| 2009 | 93.46 | 74.21 | 70.76 | 77.74 | 55.04 |
| 2010 | 93.93 | 70.89 | 68.78 | 80.25 | 54.34 |
| 2011 | 93.90 | 68.34 | 64.81 | 75.42 | 53.10 |
| 2012 | 93.34 | 66.12 | 66.38 | 76.26 | 62.04 |
| 2013 | 91.15 | 63.80 | 62.73 | 77.59 | 52.82 |
| 2014 | 95.29 | 62.48 | 58.30 | 75.22 | 43.39 |
| 2015 | 95.52 | 61.98 | 54.99 | 73.75 | 32.86 |
| 2016 | 95.80 | 60.42 | 49.27 | 71.82 | 23.52 |
| 2017 | 97.10 | 60.58 | 48.06 | 72.90 | 23.51 |
| 2018 | 95.62 | 60.87 | 46.13 | 75.28 | 21.51 |
| 2019 | 94.87 | 59.79 | 42.47 | 72.18 | 18.47 |
| 2020 | 90.49 | 58.26 | 35.91 | 67.76 | 16.08 |
| 2021 | 92.40 | 57.28 | 36.43 | 71.78 | 15.15 |
Trend description for A1
Emissions for all 5 key air pollutants (NH3, PM2.5, NOx, NMVOCs and SO2) in England have fallen over the latest 16 years for which annual, country-level data are available. Emissions of SO2 have seen the greatest reductions, falling by 85% between 2005 and 2021. Emissions of NOx, NMVOCs and PM2.5 have also fallen considerably, by 64%, 43% and 28% respectively; and emissions of NH3 have fallen by 8% over the same period.
More recently, while annual emissions of SO2 and NOx have continued to fall substantially, the rates of decline in annual emissions of PM2.5 and NMVOCs have reduced and the trend for annual emissions of NH3 has levelled off.
Assessment of change
Assessments for 4 of the air pollutants measured by the A1 indicator (PM2.5, NOx, NMVOCs and SO2) have shown an improvement in the most recent short, medium and long-term time periods. However, although emissions of NH3 are also assessed as improving over the long term, more recent fluctuations have resulted in an assessment of ‘little or no change’ over the medium and short term. More detailed reporting mentioned in the ‘Readiness and links to data’ section for this indicator may provide insights into the factors behind this change in NH3 emissions. This assessment does not consider whether any improvement is on a sufficient scale for meeting targets. Projections towards air emissions targets set at a UK scale are available to supplement this assessment.
Change since 2018 has also been assessed. There has been a decrease (improvement) in the emissions of all 5 air pollutants included within this indicator. However, this result is based on only 4 data points so should be considered as indicative and not evidence of a clear trend.
Further information on this assessment, along with details on the methodology, is provided in the Assessment background page. Summaries by 25 Year Environment Plan goal and information on indicator links are presented in the Assessment results pages.
Table A1: Assessment of change
| Component | Subcomponent | Period | Date range | Percentage change | Smoothing function | Assessment of change |
|---|---|---|---|---|---|---|
| A1 | NH3 | Short term | 2015 to 2020 | -2.42 | Loess | Little or no change |
| A1 | NH3 | Medium term | 2010 to 2020 | -0.15 | Loess | Little or no change |
| A1 | NH3 | Long term | 2005 to 2020 | -7.75 | Loess | Improvement |
| A1 | NMVOCs | Short term | 2015 to 2020 | -5.20 | Loess | Improvement |
| A1 | NMVOCs | Medium term | 2010 to 2020 | -18.62 | Loess | Improvement |
| A1 | NMVOCs | Long term | 2005 to 2020 | -42.52 | Loess | Improvement |
| A1 | NOx | Short term | 2015 to 2020 | -29.98 | Loess | Improvement |
| A1 | NOx | Medium term | 2010 to 2020 | -45.19 | Loess | Improvement |
| A1 | NOx | Long term | 2005 to 2020 | -62.69 | Loess | Improvement |
| A1 | PM2.5 | Short term | 2015 to 2020 | -4.33 | Loess | Improvement |
| A1 | PM2.5 | Medium term | 2010 to 2020 | -9.51 | Loess | Improvement |
| A1 | PM2.5 | Long term | 2005 to 2020 | -30.48 | Loess | Improvement |
| A1 | SO2 | Short term | 2015 to 2020 | -54.30 | Loess | Improvement |
| A1 | SO2 | Medium term | 2010 to 2020 | -72.36 | Loess | Improvement |
| A1 | SO2 | Long term | 2005 to 2020 | -84.29 | Loess | Improvement |
Note that assessment categories for short, medium and long term were assigned based on smoothed data so percentage change figures in Table A1 may differ from unsmoothed values quoted elsewhere. Percentage change refers to the difference seen from the first to last year in the specified date range.