Mayor of London issues high pollution alert
The Mayor of London, Sadiq Khan, has triggered a ‘high’ air pollution alert for London tomorrow, Monday, 22nd June 2026.
Forecasters at Imperial College London advised the Mayor to issue the alert and Sadiq is encouraging everyone in the capital – particularly those who are most vulnerable - to look after themselves and for everyone to do their bit.
Londoners are urged to stop their engines idling and avoid burning garden waste – which can all contribute to high levels of pollution.
Drier conditions have also potentially increased particulate matter. To help reduce the impact of air pollution on your health consider walking or exercising in parks or other green spaces, if you are not affected by pollen.
All Londoners can also do their bit to reduce air pollution by:
- walking, cycling and using public transport more frequently
- driving less, and when you do drive, drive smarter – car share if you can, turn your engine off when you're not moving, and keep your vehicle well maintained
- composting or taking garden waste to a refuse centre rather than burning it
- avoiding unnecessary burning at home – for example, using a wood burner or open fire
Whilst the pollution alert is not directly related to increased temperatures, an amber warning for extreme heat has been issued by the Met Office with temperatures forecast to hit as high as 38C on Tuesday.
To help cope with the heat, stay hydrated. There are 4,000 free water refill points and more than 100 water fountains across our city. If you need some respite from the hot weather, take a break and cool down using our Cool Spaces map.
Look out for those who may be less able to cope in the heat, including young children, babies and toddlers, older people and those with a health condition and follow the advice from NHS London.
This is the second high air pollution alert this year. Additional details have been shared with London’s GPs and emergency departments, to ensure that they have crucial information to help vulnerable patients.
City Hall issues alerts to Londoners, schools, and London boroughs when moderate, high or very high air pollution is forecast. High air pollution alerts are also displayed at public locations across London, including all bus stop countdown signs, as well as on the Underground.
The Deputy Mayor for Environment and Energy, Mete Coban said: “Toxic air is responsible for thousands of premature deaths in London each year, which is why the Mayor has done everything in his power to tackle it, which includes launching the world’s largest clean air zone.
“We are urging Londoners to look after themselves during this period of hot weather and elevated pollution levels, stop their engines idling, and refrain from burning garden waste – all of which contribute to high levels of pollution.
“It is really important we all do our bit to protect those who are most vulnerable as we continue working to build a safer and greener London for all.”
Notes to editors
- See our Cool Spaces map: https://apps.london.gov.uk/cool-spaces/
- Be aware that some Londoners will find it more difficult to cope in the hot weather, such as older people, babies and infants, and those with a health condition. https://www.nhs.uk/live-well/seasonal-health/heatwave-how-to-cope-in-hot-weather/
- Forecasters at Imperial College London advised the Mayor to issue the alert due to the likelihood of increased levels of ground-level ozone. This is caused by strong sunshine triggering reactions between existing pollutants, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs). They have also raised the potential for increased particulate matter due to the drier conditions, but this is unlikely to exceed moderate levels.
- Nitrogen oxides (NOx) are a group of gases made up of nitrogen and oxygen. They are primarily produced during high-temperature combustion processes, such as in vehicle engines, power plants, and industrial activities.
- Volatile organic compounds (VOCs) are a wide range of carbon-based chemicals that easily evaporate into the air at room temperature. They come from sources such as vehicle exhaust fuels (petrol/diesel), solvents, industrial processes and natural sources e.g. vegetation.
- Ground‑level ozone is mainly caused by a combination of pollution, sunlight, and weather conditions. It’s not emitted directly, rather, it forms in the air through chemical reactions.
- The moderate and high daily thresholds are based on Defra’s national Daily Air Quality Index (DAQI).
- Particulate Matter (PM) is a transboundary pollutant and therefore concentrations are heavily influenced by meteorology, background concentrations and sources outside of London, including on the continent, on top of local emissions.
- These thresholds are nearly two and a half times higher than the World Health Organization (WHO) recommended limits for exposure and represent especially acute exceedances which can have immediate health impacts for individuals with pre-existing conditions such as asthma or chronic obstructive pulmonary disease (COPD).
- In 2016, the Mayor set up a system to warn Londoners about moderate and high pollution episodes. These forecasts are created by Imperial College London, and checked against other public forecasts (airTEXT, Met Office, London Air) to predict when air pollution in the capital will reach moderate, high or very high levels.
- In 2024, the Mayor expanded the alerts system coverage to also go to NHS GPs and Emergency Department consultants, in order to support the health and care system across London in advising vulnerable patients.
- More information about the alerts can be found here: https://www.london.gov.uk/programmes-and-strategies/environment-and-climate-change/pollution-and-air-quality/monitoring-and-predicting-air-pollution