What is air pollution?
The European Environment Agency defines air pollution as "the presence of contaminant or pollutant substances in the air at a concentration that interferes with human health or welfare, or produces other harmful environmental effects."
The main source of air pollution is fossil fuel combustion, the central process for most electricity generation, heating systems and motor vehicles.
There are a vast range of air pollutants, which cause a variety of effects on the environment and health.
Air quality is key to the health of humans and ecosystems. Air pollution can lead to a variety of respiratory diseases, tuberculosis, bronchitis, heart and chest diseases, stomach disorders, and cancers. There is also growing understanding of the links between atmospheric problems such as local air pollution, acid rain, global climate change and stratospheric ozone depletion.
Air pollution is worst in Latin America and Asia. In cities such as Seoul and Mexico City, the air quality is so bad that some people wear facemasks to filter the air.
Air pollution has historically been caused by industrialisation and the consequent proliferation in the use of 'fossil fuels' (and therefore sulphur dioxide emissions) in the industrial process.
In modern Britain, traffic is the major air polluter, with traffic fumes accounting for just over half of the total domestic nitrogen emissions. Petrol and diesel-engine motor vehicles emit a wide variety of pollutants, mainly carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs) and particulates (PM10), which have an increasing impact on urban air quality.
The UK Government and the devolved administrations published the Air Quality Strategy for England, Scotland, Wales and Northern Ireland on 17 July 2007 - setting out a way forward for work and planning on air quality issues and the air quality standards and objectives to be achieved; introducing new policy framework for tackling fine particles and identifying potential new national policy measures which modelling indicates could give further health benefits and move closer towards meeting the Strategy's objectives.
The EU National Emission Ceilings Directive sets ceilings for each Member State for emissions of ammonia, oxides of nitrogen, sulphur dioxide and volatile organic compounds (VOCs). These four pollutants are primarily responsible for acidification, eutrophication and ground-level ozone. The ceilings must be met by 2010.
And the EU Air Quality Framework Directive (96/62/EC) defines the policy framework for 12 air pollutants known to have a harmful effect on human health and the environment. The limit values for the specific pollutants are set through a series of Daughter Directives.
A new Air Quality Directive came into force in June 2008, to be transposed into national legislation by June 2010. The Directive allows Member States to request, under strict conditions, time extensions to meet the air quality standards for PM10 (until 11th June 2011) and NO2 and benzene (until 2015 at the latest).
Work is currently underway to review the Gothenburg Protocol which came into force in 2005, setting targets for reducing pollutants and emissions which were to be met by 2010. More non-EU countries are being encouraged to sign up to the protocol which will set new emission ceilings for 2020.
Concerns about air pollution range from the very local - many rural and suburban councils cite the nuisance caused by bonfires as their principal air pollution problem - to the truly global. Pollution crosses national boundaries and international action, which is not always forthcoming, is required to address it. Moreover, evidence of climate change, caused by air pollution, suggests that pollution's effects may be irreversible and catastrophic.
Environmental concerns have only become mainstream in the developed world's political systems in the last 20 years or so, but many still claim that economic objectives are routinely given precedence over the environment. In the developing world, which is increasingly industrialising, the problem is becoming even more pressing.
Air pollution in the UK is cited as a contributing factor in a range of environmental and health problems, such as rising rates of childhood asthma, allergies and habitat loss, although its precise role is frequently vaguely defined.
Environmental group Friends of the Earth claimed that air pollution in London breached legal limits in April 2011, despite commitments by both the UK Government and the London Mayor to bring it under control to avoid huge EU fines. FoE called.on London Mayor Boris Johnson to "take urgent action to cut traffic and encourage people to walk, cycle and use public transport more frequently."
The UK has met current international targets to reduce total emissions by 2010 of four air pollutants that cause harm to people’s health and to the natural environment.
Emissions of sulphur dioxide have fallen by 89 per cent between 1990 and 2010, but increased by 2 per cent between 2009 and 2010. Emissions in 2010 were 31 per cent below the lowest international target for the UK.
Emissions of nitrogen oxides have fallen by 62 per cent between 1990 and 2010, and fell by 3 per cent between 2009 and 2010. Emissions in 2010 were 5 per cent below the lowest international target for the UK.
Emissions of non-methane volatile organic compounds have fallen by 71 per cent between 1990 and 2010, and fell by 4 per cent between 2009 and 2010. Emissions in 2010 were 34 per cent below the international target for the UK.
Emissions of ammonia have fallen by 21 per cent between 1990 and 2010, but increased by 0.5 per cent between 2009 and 2010. Emissions in 2010 were 4 per cent below the international target for the UK.
Source: Defra: National Atmospheric Emissions Inventory (NAEI) – December 2011
"Air pollution in the UK has declined significantly over recent decades through measures to reduce pollution from transport, industrial and domestic sources. However, the rate of reduction is now levelling off for some key pollutants such as oxides of nitrogen."
Defra - 2011
"It's outrageous that London is choking on air so dirty it's illegal - air pollution contributes to thousands of premature deaths every year in the capital, particularly affecting some of its most disadvantaged people.
"Mayor Boris Johnson must improve air quality by prioritising funding for measures that will get Londoners driving less and walking, cycling and using public transport more - and scrap traffic generating schemes like new road crossings over the river Thames."
Friends of the Earth London Campaigner, Jenny Bates – April 2011