This was the story told by provisional figures for the government’s air quality indicator for sustainable development, released by the Environment Department (DEFRA) in late January.1 Last year was the first time measurements have been taken from new monitoring stations put in place to reflect a 2008 EU Directive on air quality. More emphasis has been placed on roadside locations and less monitoring of carbon monoxide and sulphur dioxide. More sites now monitor nitrogen dioxide (NO2) and ozone.
The level of PM10 in urban background locations averaged 20 micrograms per cubic metre over the year, down by 2µg/m3 the previous year. At more polluted roadside locations, the mean level was 28µg/m3.
Although levels varied in recent years due to the weather, both measurements have recorded a general decline in air quality since records began in the 1990s.
Average levels of ozone in towns have been rising since the early 1990s, from 44µg/m3 in 1992 to the record of 61 µg/m3 in 2006. Levels in 2008 reached a joint-second highest figure of 60µg/m3. The increases are thought to be an unwelcome effect of reduced levels of NO2, which destroys ozone.
In contrast, ozone pollution in the countryside has persisted at an average of about 70µg/m3 since the late 1980s.