Pollutants of concern
Pollution from road traffic, and especially diesel engines, is the most significant cause of poor air quality, responsible for up to 70% of air pollution. Emissions from power stations are also important, particularly sulphur dioxide. The pollutants of most concern in urban areas are:
- Microscopic airborne particles of varying sizes and composition, known as particulate matter (PM), suspended in the air
- Various nitrogen oxides (NOx) emitted by road vehicle engines and other combustion processes, which are converted to nitrogen dioxide (NO2)
- Ozone formed through the reaction of NOx with sunlight
Deprived areas in cities typically experience heavier than average traffic. As a result, the detrimental effects of air pollution tend to have a greater impact on people living in deprived urban areas, who already suffer disproportionately from health inequalities.
Short and Long-Term Exposure
Both short-term and long-term exposure to air pollution have adverse health effects. The previous Government recognised the impact of short-term exposure to high levels of pollutants when it included poor air quality events in the 2015 Risk Register. The register states that these events can lead to additional deaths and a reduction in life expectancy for people affected.
In 2009 the Government Advisory Committee on the Medical Effects of Air Pollutants (COMEAP) concluded that concentration of PM2.5 (particles that are between 2.5 thousandths of a millimetre in diameter or less) was the best measure for quantifying the mortality effects of long-term exposure to particulate air pollution.
The International Agency for Research on Cancer, a WHO organisation, concluded in 2012 that diesel exhaust is a cause of lung cancer. A Review of evidence on health aspects of air pollution by the WHO in 2013 confirmed a link with effects on respiratory and cardiovascular systems. It also noted emerging evidence of other effects, including on the endocrine system and the nervous system.
In 2015 COMEAP examined studies linking long-term exposure to NO2 to increased respiratory and cardiovascular mortality, and children’s respiratory symptoms. It concluded that it would be sensible to regard NO2 as causing some of the health impacts associated with air pollution in epidemiological studies.
Local authorities are responsible for managing air quality at a local level. However, some decisions made to reduce carbon dioxide emissions at a national level, in particular the comparatively favourable tax treatment of vehicles with diesel engines, have proved detrimental to urban air quality.
Diesel vehicles produce around 22 times more particulate matter and four times more nitrogen oxides than petrol vehicles. Reversing these trends will take time, and there have been calls, including from the Mayor of London and the Environmental Audit Committee, for financial incentives to accelerate this. These include extending low emissions zones, amending fuel duty or providing grants for scrapping older diesel cars.
Court and EU infraction proceedings
The need to improve air quality is recognised in EU legislation, which sets limits for a range of pollutants. As part of this member states were required to prepare adequate plans to reduce NO2 to acceptable levels by 2010, or 2015 at the latest. The UK failed to do so.
Currently legal limits for NO2 will not be met in 16 of the UK's 40 air quality zones until after 2020, including Greater Manchester and Leeds. In London, the limits will not be met until after 2025.
The Government's failure to meet NO2 targets led to ClientEarth, a UK charity, taking the Government to court. They argued against the UK’s position that enforcement of air quality measures lay at EU level.
The Supreme Court agreed with them, and after referral to the Court of Justice of the EU in 2013 for clarification set out its ruling on 29 April 2015. The Court unanimously ordered that the Government must submit new air quality plans to the European Commission no later than 31 December 2015.
Separately, in February 2014 the EU Commission began infraction proceedings against the UK. These could take several years and could result in the UK Government being fined. Should this occur, it would be the first time the UK Government has been fined by the EU for breaching legislation.
However, since 2011, under the Localism Act, the Government has discretionary powers to pass all or part of any fines on to local authorities deemed responsible for breaches of EU legislation.
The previous Government wrote to all local authorities in March 2014 to inform them of the infraction proceedings and remind them of these powers.
- Conservatives: will continue tackling air pollution
- Greens: introduce Ultra Low Emission Zones to ensure air pollution reduces to comply with EU limits
- Labour: will tackle air pollution by giving local authorities the powers they need, backed up by a national framework
- Liberal Democrats: will pass a Green Transport Act, including a National Plan to improve dramatically Britain's air quality by 2020