GLA - Dramatic improvements in air quality on London’s roads 

23 April 2020
"London has one of the most advanced air quality monitoring networks in the world, which has recorded how the coronavirus lockdown has dramatically improved air quality in London"

The Mayor of London, Sadiq Khan, has today published new evidence which shows dramatic improvements in air quality as a result of the halving of traffic in London due to the coronavirus lockdown. This is in response to environment ministers' call for evidence which will feed into the Government's response to COVID-19.  

The Mayor has already made huge strides in cleaning up London's air, including introducing the world's first Ultra Low Emission Zone (ULEZ) in central London. Reductions measured in recent weeks are in addition to the significant improvements delivered since 2016. A report on these improvements has been published today to provide important context to the COVID-19 reductions. The report also confirms the effectiveness of clean air zones in tackling air pollution. 

In 2020, before measures to address the COVID outbreak were introduced, hourly average levels of harmful gas nitrogen dioxide NO2 at all monitoring sites in central London had already reduced by more than a third (35 per cent) compared to the same period in 2017. Since 16 March 2020 there has been an additional reduction of 27 per cent.  

Poor air quality stunts the growth of children's lungs and worsens chronic illness, such as asthma, lung and heart disease. There is also emerging evidence linking air pollution with an increased vulnerability to the most severe impacts of COVID-19*.  

The report shows:   

There have been huge reductions in NO2, especially at roadside sites. Central London roadside locations have seen a fall in daily average NO2 of around 40 per cent. These reductions are in addition to those already delivered by the ULEZ.   

One of London's busiest roads, Marylebone Road, has seen a reduction in daily average NO2 of 48 per cent and Oxford Street has seen a reduction of 47 per cent.  

Despite these improvements, London has had particulate pollution episodes during lockdown. This exposes that London's poor air quality is not just the result of traffic pollution and further action is required on other sources, including domestic burning and agricultural emissions.  

Evidence from the Breathe London air quality monitoring network will also be submitted to the Department for Environment, Food and Rural Affairs (Defra), which shows similar reductions in NO2 across the city. The Breathe London team have used Waze for Cities data to measure big reductions in congestion.  

This is part of efforts by a number of world cities better to understand the impacts of COVID-19 lockdown measures on air quality. London is working closely with the C40 Cities Climate Leadership Group to share information and best practice.   

 City Hall has also today published new data showing dramatic improvements in London's air quality across the capital since 2017.  

 The report reveals that the introduction of policies including the world's first ULEZ have contributed to a reduction of 44 per cent in roadside NO2 in the central London ULEZ zone**. In January there were 44,100 fewer polluting vehicles being driven in the central zone every day with 79 per cent of vehicles in the zone now meeting the ULEZ emissions standards - up from 39 per cent in February 2017***.  

Around half of London's air pollution comes from road transport. Today's evidence shows how our polluted air is often caused by the way we choose to move around the city. Nearly half of car trips made by Londoners before the coronavirus lockdown could be cycled in around ten minutes.**** 

The Mayor of London, Sadiq Khan, said: "London has one of the most advanced air quality monitoring networks in the world, which has recorded how the coronavirus lockdown has dramatically improved air quality in London. But this cleaner air should not just be temporary, as Londoners deserve clean air at all times. So once the current emergency has passed and we start to recover, our challenge will be to eradicate air pollution permanently and ensure the gains we've made through policies such as ULEZ continue. It is critical that Government keeps this in mind as part of the country's recovery from the pandemic." 

Senior Manager Air Quality at the Environmental Defense Fund Europe, Elizabeth Fonseca, said: "People with certain serious medical conditions are at higher risk for severe illness from Covid-19, so it's critical to keep in mind the health impact of pollution, both as people are experiencing it now and long-term. Nitrogen dioxide pollution has gone down, but London recently saw huge spikes in dangerous particulate pollution. A few weeks or months' improvement of just one pollutant doesn't make lung disease and other ailments disappear."  

Senior Lecturer in Air Pollution Measurement at King's College London, Dr Gary Fuller, said: "Breathing bad air has had an intolerable impact of Londoner's health for far too long. In our operations centre at King's we have  been measuring London's air pollution for nearly 30 years. During this time we've seen deteriorations followed by a long period when some places showed slow improvement, and others slowly worsened. For years it felt like we were at a standstill.

"But, even before the Covid lockdown, London's air pollution was undergoing a dramatic change for the better. Nitrogen dioxide in central London and along main bus routes was improving at some of  the fastest rates we've ever measured. We need to remember these lessons going forward. These successes show that our city's air pollution is not an intractable problem and that actions can bring results."

Royal College of Physician Special Adviser on Air Quality, Professor Stephen Holgate, said: "A year ago who would have believed our lifestyles would have changed so dramatically? Who would have believed it possible that the toxic air pollution in our capital city would be cut by half as a result of ULEZ and a drastic decrease in travel?

"While COVID-19  has wreaked havoc in our lives, this dreadful virus has brought the importance of outdoor space and the environment into focus. The consequences of this virus will be significant and felt for many years to come. However, as people's behaviours have changed, we have seen real improvements in air quality. We're all looking forward to the time when the lockdown is lifted, and once it does, I sincerely hope we'll be able to retain some of the new cleaner and greener habits we've developed."  

Notes to editors

* Harvard University research linking air pollution with an increased vulnerability to the most severe impacts of COVID-19 - Similarly, in the UK the University of Cambridge have found links between levels of air pollution and the severity of COVID-19 (

 **This is measured from February 2017 to January 2020, to reflect when the Mayor publicly confirmed the Toxicity Charge (T-Charge) - the predecessor to the ULEZ - and people started to prepare for the schemes.   

 *** The 79 per cent compliance rates in January 2020 refers to a 24 hour period. Before the introduction of the ULEZ 24 hour compliance data was not available so data from Congestion Charging hours was used as a proxy instead.   

**** Nearly half of car trips made by Londoners before the coronavirus lockdown could be cycled in around ten minutes 

The Mayor's response to the Defra call for evidence is available here:

The ULEZ report is available here:

Analysis of the impact of COVID-19 measures using the Breathe London network is available:

The evidence shows that road traffic in London has reduced by around 50 per cent Londonwide since the beginning of March.  

In February 2017 the Mayor confirmed the introduction of the T-charge as a stepping-stone for the ULEZ and this can be seen as the start of the accelerated change in the vehicle fleet as Londoners and businesses prepared for the new schemes and buses on routes in central London began to be upgraded to become ULEZ compliant. 

London has one of the most advanced and comprehensive network of air quality monitors. The analysis has used data from more than 100 fixed air quality monitors, alongside the Breathe London network, which has 100 state-of-the-art fixed sensor pods mounted on lampposts and buildings close to known air quality hotspots and sensitive locations such as schools and nurseries. 

Maintaining air quality monitoring stations has been designated essential work by the Environment Agency and the Greater London Authority.