Frequently Asked Questions

Please see the Breathe London Methodology page.

Please see the Breathe London Methodology page.

Please see the Breathe London Methodology page.

All pollutants we measure are harmful to human health and have known association with adverse health outcomes. Some of the pollutants are also important contributors to climate change.

See our Air Pollution webpage for more information about sources and health effects of these pollutants.

Stationary Monitoring: Carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2), particulate matter (PM) in various size cuts (PM2.5 and PM10 are reported) and, in some locations, ozone (O3).

Mobile Monitoring: Black carbon (BC), CO2, NO, NO2, O3, PM2.5 (and other PM size cuts) and ultrafine particles (UFP).

Breathe London’s approach reveals the locations and potential sources of pollution at a more granular spatial resolution than the traditional government monitoring networks.

The European Air Quality Directive has defined Data Quality Objectives (DQOs) for various air-pollution monitoring methods. The DQOs mandate that regulation and enforcement use regulatory-grade monitors, which provide higher certainty than lower-cost sensors like Breathe London’s AQMesh pods. However, the directive also recognises that indicative measurements – such as those made with the AQMesh pods – are useful in identifying geographic and temporal trends.

Therefore, the sensor pods complement the existing monitors and add another, more localised layer of air pollution information. EDFE, our technical partners and the Greater London Authority believe filling in this spatial gap in London’s air monitoring network is a critical, near-term step to tackling the city’s air pollution problem.

Near real-time data from the stationary monitors will appear on the Breathe London map as it becomes available. You can download the stationary monitoring dataset for NO2 here and PM 2.5 here. You can download mobile monitoring data from the Google Street View cars here.

You can also view and download the data on Environmental Defense Fund’s Air Quality Data Commons, which seeks to accelerate solutions to air pollution by standardizing and sharing air quality data.

Breathe London’s air pollution data API is now available for public use. If you are interested in developing your own third-party app and/or service please contact the project team on hello@breathelondon.edf.org with details of your request. Further information and instructions can be found via the API documentation.

The Breathe London map shows the contribution of different sources of NOx pollution at monitoring sites across the city. The data on the map is based on the ADMS model setup for a ‘standard’ emissions scenario, using 2013 London Atmospheric Emissions Inventory (LAEI)* data for 2018 modelling hourly concentrations in µg/m3 from 1st April 2019 to 12th December 2019; this is described in more detail on the Methodology page under the topic ‘Identifying local pollution sources’.

The following table shows the 5 pollution source categories that can be explored on the map and a brief description of each source that was modelled.

*The 2013 LAEI was published in 2016.

Air quality can vary substantially depending on where you are in the city. The project team is currently assessing the preliminary data and will share insights on a regular basis. Initial analysis from the first 9 months of operation indicated that nearly half of the sites measured by Breathe London are at risk of illegal air pollution levels for nitrogen dioxide..

Please sign up for updates or follow us on Twitter at @Breathe_London.

At each sensor site, we provide the current average pollution levels, as well as pollution levels measured since the beginning of the project. We also provide the World Health Organisation’s (WHO) short-term guidelines (recommended limits for daily or hourly exposure to a given pollutant) and long-term guidelines (limits for annual exposure). Most of the stationary data presented here are averaged over an hour.

Breathe London refers to the WHO guidelines as they are the most protective available. Although the WHO guidelines are not legally binding, they have been developed by public health experts based on substantial research to help the UK and other governments set pollution limits for protecting human health. See more at WHO Air Quality Guidelines.

The Breathe London project is studying the accuracy of these lower-cost sensors to better understand how they compare to more costly and bulky ‘reference monitors.’ Until the study is complete, the data is provisional and comparison to any health criteria guidelines should be considered indicative only.

Millions of Londoners face health threats every day because of air pollution. WHO recommends maintaining concentrations of air pollution that are as low as possible, especially to protect sensitive groups such as children, older people or people with pre-existing health conditions. Recent evidence indicates that exposure below the standards may also affect health.

Breathe London’s granular, local monitoring is essential for designing the targeted, robust and durable solutions needed to reduce pollution. That’s the next step, but we have to collect the data first to make London a safer place for kids and people of all ages to live.

Please see our Take Action page.

When the Breathe London monitoring network identifies a likely hotspot, the relevant local authorities (the Greater London Authority, borough council or other) can perform further testing as needed, and then take action via immediate remediation or a longer term policy solution.

Analysis of data from this project can be used to assess and inform new policies and other solutions for reducing air pollution. The Breathe London project team plans to use a combination of stationary and mobile monitoring data along with air quality models to:

• Provide baseline data to paint a clearer picture of air pollution across London.
• Provide information on sources and what is driving air pollution concentrations across the city.
• Measure air pollution within and outside central London before and after the implementation of the Ultra Low Emission Zone (ULEZ), in order to help assess the effectiveness of this flagship policy from the Mayor.
• Improve London’s current air quality models, providing a more accurate picture of the pollution Londoners are exposed to throughout the day.
• Improve the ability to forecast episodes of high pollution; design policies that respond to these episodes, such as tighter controls on fossil fuel burning or restrictions on access to urban areas for polluting vehicles.

Data from the Breathe London project could also be used in a variety of other ways to assess and improve air quality. Some examples include:

• Measure the impacts of a variety of policy interventions – including School Streets street closures, low-emission neighborhoods, low-emission bus zones and others.
• Inform air quality plans to help local authorities and schools in the most polluted areas reduce pupils’ exposure to hazardous pollution.
• Support development of planning policy to ensure new schools and other buildings used by vulnerable populations are not located in areas of poor air quality.
• Inform controls on air pollution from construction sites and other sources.
• Highlight the areas where new interventions are needed most.
• Improve clean air route mapping and transport choices.

Introduced in April 2019, the ULEZ charges most older vehicles – which have less efficient engines and pollute more – extra to enter Central London. The ULEZ builds on London’s existing efforts to curb traffic and improve air quality, including the congestion charge that was introduced in 2003. Learn more.

The air quality alerts provided on our map are based on forecasts of expected air quality produced by CERC’s ADMS-Urban air quality model. These alerts use Defra’s Daily Air Quality Index (DAQI) which tells you about levels of air pollution and provides recommended actions and health advice.

The Breathe London map incorporates air quality alerts that show forecasts for tomorrow and the day after for each London borough. You can also sign up here to receive these free airTEXT alerts and forecasts.

The alerts are separated into different levels (including ‘no alert’, ‘moderate’, ‘high’ and ‘very high’) based on the highest concentration of five different air pollutants: Nitrogen Dioxide (NO2), Particulate Matter (PM10), fine Particulate Matter (PM2.5), ozone and Sulphur Dioxide (SO2).

Air quality alerts are designed to help ensure you can plan ahead and, if possible, reduce your exposure. If you suffer from a medical condition, like asthma, which can be made worse by air pollution, these alerts also provide some notice so that you may have any necessary medication at hand. The air pollution levels and health advice shown in the table below are based on Defra’s DAQI and provide two sets of advice, one for at-risk individuals* and the other for the general public.

The 3 steps below are recommended to use the DAQI.

Step 1: Determine whether you (or any children or adults under your care) are likely to be at-risk from air pollution. You may find more information here and your doctor may be able to give you advice.

Step 2: If you may be at-risk, and are planning strenuous activity outdoors, check the air pollution forecast.

Step 3: Use the health messages in the table below corresponding to the highest forecast level of pollution as a guide.

*Adults and children with heart or lung problems are at greater risk of symptoms. Follow your doctor’s usual advice about exercising and managing your condition. It is possible that very sensitive individuals may experience health effects even on “no alert” air pollution days.

Long-term effects of air pollution

While the air pollution alerts and health advice above are geared towards the effects from short-term exposure to high levels of pollution, it is important to note that long-term exposure to air pollution can cause chronic conditions which may lead to reduced life expectancy. You may find more information on the long-term health effects of air pollution in the 2018 Guidance published by Public Health England.

Please see our Take Action page.

Unfortunately, the project locations have already been selected and it is not possible at this stage to add any additional monitors.

Contact hello@breathelondon.edf.org for more information.