London Mayor announces air quality initiative
The Mayor of London, Sadiq Khan, on Wednesday called on ministers to follow London’s leadership and adopt a legally binding target of meeting the World Health Organisation (WHO) air quality guidelines by 2030. Sadiq Khan also announced a £25 million polluting vehicle scrappage scheme for low-income and disabled Londoners.
Campaigners argue that in the UK, air quality is a national health crisis. Data from the European Environment Agency (EEA) showed that British citizens were suffering from over 44,000 premature deaths a year due to harmful exposure from particulate matter, nitrogen dioxide and ozone. The most common reasons for premature death are heart disease and stroke. This is followed by lung diseases and lung cancer. For children, short-term and long-term exposure to air pollution can lead to reduced lung function, respiratory infections and aggravated asthma. Ambient air pollution is also associated with adverse impacts on fertility.
Tackling air pollution hinges on a good understanding of its causes
Effective policy action to reduce air pollution requires a sound understanding of the main air pollutants and their main sources. A holistic approach can ensure overall air quality is being reduced and not just a constituent part. For example, extensive government research has shown that dissuading polluting vehicles from city and town centres is by far the quickest, most cost-effective way to cut levels of nitrogen dioxide (NO2) in urban areas. This measure, however, would not be as effective at reducing particulate matter emissions.
Key primary air pollutants include particulate matter (PM), Nitrogen Oxide (NOx), Sulphur Oxide (SOx), Ammonia (NH3), Carbon Monoxide (CO) and Non-Methane Volatile Organic Compounds (NMVOC). There are many sources of air pollution, including (but not limited to) power stations, transport, household heating, agriculture and industrial processes.
Figure 1: UK emissions of nitrogen oxides (NOx) by sector in 2017 (DEFRA)
Around a third of NOx emissions come from cars, particularly old diesel cars. This is followed by emissions from energy industries and the manufacturing & construction sectors that, for some processes, use gas oil and fuel oil – these fuels have a higher NOx intensity compared to natural gas.
Domestic heating accounted for only 11% of total NOx emissions. This is largely due to a high percentage of homes using natural gas (lower NOx intensity compared to heating oil) to satisfy space and heating demand and stricter boiler emission requirements from European directives such as Ecodesign.
Figure 2: UK emissions of particulate matter emissions (PM10 and PM2.5) by sector in 2017 (DEFRA)
It’s a different picture entirely for particulate matter emissions. Domestic heating is a major source of PM emissions, accounting for 27% and 41% of PM10 and PM2.5 respectively. Most emissions from this source come from burning wood and other solid fuels in closed stoves and open fires. The use of wood in domestic combustion activities accounted for 36% of PM2.5 emissions in 2015. Earlier this year DEFRA stated its intention to move to provide local authorities with more power over smoke control zones, regulate for cleaner solid fuels and encourage use of kiln dried wood for home burning, all of which could make a significant difference for particulate matter.
Road transport only accounts for 11% of PM10 emissions and 12% of PM2.5 emissions. This has been driven by a marked reduction (~83% on 1996 levels) in exhaust emissions due to stricter emission standards. However, this has been partially offset by an increase in non-exhaust emissions from braking and tyre & road wear from increased traffic activity.
What does this mean for policy?
Air pollution needs direct and effective action to tackle the widespread sources of air pollution which stem from the transport, building, energy and industrial sectors. Sector-specific solutions and policies should be developed to accelerate the reduction in air pollution and to reduce the eye-watering £20 billion a year cost to the UK economy.
Curbing air pollution will require collaboration and coordinated action at national and local levels, in tandem with other climate and sectoral policies.
For more information please contact Faisal Haroon
 Air Quality in Europe: 2019 – European Environment Agency
 Review of evidence on health aspects of air pollution (technical report) – World Health Organisation
 UK Plan for tackling roadside nitrogen dioxide concentrations (technical report) – Department for Transport
 EMEP/ EEA air pollutant emission inventory guidebook 2016 (updated July 2017) – EEA
 PM emissions vary in size and are classed as PM2.5 and PM10 – the numbers indicate the diameter or the width of the particle. So PM2.5 means the mass per cubic metre of air of particles with a size (diameter) generally less than 2.5 micrometres.