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Imperial College London worked with Global Action Plan and the Cross River Partnership to measure the impact of anti-idling days. On designated 'clean air action days', teams of trained volunteers approached drivers of parked vehicles at locations across London to positively engage with them and ask them to switch their engines off. Over the two action days, hundreds of drivers were engaged and the project reached almost 4 million people online. The results indicated that the most significant impact could be detected in locations where the monitor could detect a strong signal from the parking bay and where anti-idling action was focused at that location. At these locations a reduction of between 20-30% in peak concentrations was observed. For more information, read the full report here.
There are some studies that have suggested that greening of highly polluted streets can significantly reduce pollution, but there is little validation of this research and numerous other studies have not supported this idea. Overall, these solutions are too small compared to the magnitude of the problem and can, in certain circumstances, make things worse. Trees planted along roads can limit the dispersion of pollutants away from the roadside and certain plants are high emitters of volatile organic compounds during the summer months that contribute toward ozone generation. However, it is a politically appealing solution, because it provides an apparent alternative to targeting and legislating against the polluter/vehicle owner. There are many other benefits of greening the environment, but the potential impacts on urban air quality have been overstated.
There are many 'low cost' sensors entering the market, but the technology is still developing and has some issues, which can cause misleading results. Monitoring air pollution can be a complex and expensive task and there is not one sensor that we can fully endorse at this time. Sensors may be capable of showing high concentrations, but will not necessarily pick up more subtle changes in pollution levels detected by more expensive equipment. For nitrogen dioxide (NO2) a well established and proven alternative is to use diffusion tubes, as used by local authorities across the country. An organisation called Mapping For Change helps local community groups do diffusion tube monitoring. Friends of the Earth supply a diffusion tube monitoring kit for a small donation.
Health Effects
Yes, studies globally show children growing up in polluted areas have smaller lungs than they should.
Yes, both the shielding effect of the building and your home's height above street level will lead to a decrease in pollution levels compared to that experienced at the road side. The amount of decrease depends on the pollutant (e.g nitrogen dioxide (NO2) drops off more than PM2.5 particulates) and weather conditions. More details on indoor pollution is in our guide.
Evidence shows that cyclists and pedestrians are often exposed to less air pollution than people in cars, taxis and buses. For coverage of our work on this see the video for a comparison. Our guide also has information on cycling and walking.
Air quality is generally worse in periods of still weather when there is less wind to disperse pollution. Ozone is formed when nitrogen dioxide and other chemicals react with sunlight. Therefore we get elevated concentrations of ground level ozone in spring and summer when the sunshine is stronger. Summer smog occurs when ozone mixes with particles, and it typically occurs during hot weather in built up urban areas and the surrounding countryside. Winter smog is formed when it is cold and a thin layer of the atmosphere near the earth becomes cooler than the air above it, known as temperature inversion. This layer traps local emissions at ground level until there is a change in the weather bringing a fresh influx of cleaner air and dispersing the pollution build up.
EU air pollution regulations cover 12 pollutants: fine particles, larger particles, Nitrogen dioxide (NO2), Ozone, Sulphur dioxide (SO2), Carbon monoxide (CO), Polycyclic Aromatic Hydrocarbons, Benzene and a range of metals (lead, arsenic, cadmium and Nickel). Full details can be found on the EU's air quality webpage. European Union air quality standards are based on the best available scientific knowledge at the time, where there is an overall consensus, with the aim of minimizing the harmful effects of air pollutants on human health. However, unlike the World Health Organization's guidelines, which are based solely on health impacts, the EU limits account for the feasibility of compliance and the likely economic impacts. The EU limits are therefore often set higher than the equivalent WHO or other national guidelines. For example, the EU limit for fine particles is set at 25ug/m3 as an annual mean. For the same pollutant the WHO set a limit of 10ug/m3 and the US National Ambient Air Quality Standard is 12ug/m3 (averaged over 3 years). Given that health effects of fine particles have been reported below the EU limit value, they cannot be said to protect the public from adverse health effects, they simply minimize risk. Therefore, not meeting the EU limits should be viewed in a very dim light. So are the current EU limit values fit for purpose? In terms of absolute protection of public health, probably not. As a legal mechanism to drive down emissions to reduce risk, a conditional yes.
Air pollution concentrations are combination of emissions and also their dispersion in the atmosphere. The combination of still conditions and also the morning rush hour means that the morning is often the worst time for traffic pollution. There's often a second, but smaller and broader peak in the late afternoon and evening. There are differences depending on days of the week with traffic pollution being lower on Saturdays and Sundays compared to weekdays. Another important thing to consider is ground-level ozone concentrations which normally peak in the mid to late afternoon in summertime.
Air pollution exposure to children has lifelong health consequences & worsens existing disease in the elderly
Health Advice
You can sign up to receive advance forecasts every day, or only when it's going to be polluted. You can subscribe to the London forecast , or in some surrounding areas you can get forecasts from us via airAlert. You can also get notifications if actual pollution levels at monitoring sites change through our SMART phone apps or Chrome extension . If you live or work in the City of London then you can also receive alerts by subscribing to the 'At Risk' group in the cityair app.
We haven't tested any air purifiers to date but it is important to consider running cost, noise, affected pollutants, size of room and consumables (frequency of changing and cost). The main challenge with many home air purifiers is to ensure the HEPA (High Efficiency Particle Attenuation) filters are changed at appropriate times to ensure continued efficiency. If you are worried about ambient sources penetrating your home then think about which windows you open and when. To minimise indoor sources of air pollution make sure to use extractors fans when cooking and avoid lighting candles or open fires.
London
The London Low Emission Construction Partnership (LLECP) is a collaboration between the 'Cleaner Air Boroughs' in central London and Imperial College London. The project is funded by the Mayor of London and aims to reduce emissions from the construction industry. For central London and Canary Wharf construction machinery has to meet certain emissions criteria, a so called low emission zone for construction. For more information on this, have a look at the non-road mobile machinery website.
The Nowcast is a visualisation to help people think about their daily exposures. We produce it from modelled pollution maps which we adjust with the latest air pollution data each hour. We warp the map surface profile to get the best match to the measurements and then report these according to the UK Air Quality Index. The lower panel on the nowcast page explains the process and you can access more detail from the bullet points. To make the annual pollution maps we use detailed information about London's pollution emissions, including information about traffic and traffic speeds on our roads and combine this with meteorology to predict how the pollution spreads. To find out more look at the London Atmospheric Emission Inventory on the GLA web pages.
Yes. In 2014 it was estimated that 69% of people burning wood in London were doing so in an open fire, a practice banned in the capital by smoke control areas created many years ago to avoid the smogs common in the city until the 1960s. See out Guide page on Wood Burning.
The London Air Quality Network(LAQN) was formed by the University, NHS and London boroughs in 1993 to give better information about air pollution. The LAQN is a partnership of members including local authorities (both in and around London), Business Improvement Districts (BIDs), Transport for London (TfL) and others. There is no strategic London-level funding for the work we do and for the public outputs we provide. The service is entirely funded on a 'not for profit' basis through individual contracts from the members for managing their measurement data. The LAQN database is a core resource for researchers from King's and other universities to investigate the changing sources of air pollution in the capital and how it impacts on the lives of Londoners.
Membership of the LAQN is a decision for each local authority. Whilst some authorities outside London are members, and support our public work, some inside London have opted not to be members and without funding support we only provide limited information in these areas. You can see the current list of LAQN members here. You should contact your local authority for information if you have any questions on their participation.
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Our Guide to Air Pollution, Health and Actions

We try to answer common questions about air pollution in London, and explain how our website can keep you informed.