Air quality statistics in the UK 1987 to 2017

News published: 30/04/2018

The air quality statistics for 2017 are now finalised and summarise the concentrations of major air pollutants as measured by the Automatic Urban and Rural Network (AURN). These statistics cover annual average concentrations in the UK of particulate matter (PM10 and PM2.5), nitrogen dioxide (NO2) and ozone (O3).  

They also include the number of days on which levels of any one of a set of five pollutants (PM10, PM2.5, NO2, O3 and SO2) were ‘moderate’ or ‘higher’, according to the UK Daily Air Quality Index (DAQI).

The full Defra Statistical Release is available for download, highlights are as follows:

  • Urban background and roadside particulate pollution (PM10) has shown long-term improvement, and small decreases in concentration are observed from 2016 to 2017 for both roadside and urban background sites. A substantial network for fine particulate matter (PM2.5) has been operational since 2009 which shows a similar trend.
  • The number of hours of moderate or higher levels of particulate matter (PM10/PM2.5) pollution has reduced in the long term, but a slightly greater number of hours were recorded in 2017 compared with 2016 for PM2.5 at both roadside and urban background sites. This is the first increase since the peak of the time series in 2011.
  • PM2.5 pollution tends to peak in the winter months and in the evening. The month with the greatest average concentration in 2017 was January; and the time of day with the greatest average concentration was 9pm. Burning of wood and coal by households in stoves and open fires is a large contributor to emissions of particulate matter both in the UK and across Europe, and is most common in winter months and during the evenings.
  • Urban background and roadside nitrogen dioxide (NO2) pollution has shown long-term improvement and small decreases in concentration are observed from 2016 to 2017 for both roadside and urban background sites.
  • There were on average fewer hours of moderate or higher levels of nitrogen dioxide pollution in 2017 compared with 2016 at roadside sites. This continues a trend for reduction in short-term moderate or high NO2 pollution since 2007, mainly due to reductions in this measure at monitoring sites in London.
  • In 2017, NO2 pollution tended to peak in the rush hours and during weekdays; particularly for roadside sites. Concentrations at roadside sites were 26 percent greater on a weekday compared to the weekend. This pattern of concentrations follows the daily and hourly trends in road traffic.
  • Urban background ozone (O3) pollution has remained fairly stable between 2003 and 2017, although concentrations have shown a long-term increase since monitoring began. Rural background ozone pollution has shown no clear long- term trend. Both these indicators increased slightly from 2016 to 2017; continuing the fluctuation in recent years.
  • There were on average fewer hours of moderate or higher levels of ozone pollution in 2017 compared with 2016 at both rural and urban background sites. This measure can vary greatly from year-to-year, although there has been a decreasing trend over the last decade particularly for rural sites.
  • In 2017, O3 pollution tended to peak in the spring months. Concentrations at rural background sites built up over the first few months of 2017, peaking in April before reducing to a stable level from July to the end of the year.
  • There were on average fewer days of moderate or higher pollution at urban pollution monitoring sites in 2017 compared with 2016. There is an ongoing decline in days of moderate or higher pollution at urban sites.
  • There were on average fewer days of moderate or higher pollution at rural pollution monitoring sites in 2017 compared with 2016. However, there is a great deal of year-on-year variability and there is no clear long-term trend.
  • The main drivers of the average number of days when air pollution is Moderate or higher are particulate matter and ozone, for urban and rural pollution monitoring sites in the UK respectively. In 2017, there were a greater number of days on average when air pollution was moderate or higher at rural sites compared to urban sites.

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