Mayor of London issues high pollution alert

26 February 2019

A spokesperson for the Mayor of London, said: “The high levels of pollution expected over the next few days is evidence of the scale of London’s air quality crisis and is exactly why the Mayor is taking hard-hitting measures to clean it up.

“April’s launch of the world’s first Ultra Low Emission Zone (ULEZ) in central London is expected to reduce harmful emissions in the zone by around 45 per cent. The Mayor is also cleaning up the capital’s bus and taxi fleets, rolling out rapid charging infrastructure and delivering improvements to schools in some of London’s most polluted areas”.

“The Mayor has launched scrappage schemes for micro-businesses and charities that use polluting vans and minibuses and will launch a similar scheme to help lower-income households scrap polluting cars later this year. He is calling on the Government to help fund a national scrappage scheme targeted at cities across the UK.” ends


This is the 10th time the air quality alert system has been used since Sadiq Khan became Mayor. Once for ‘Very High’ and nine times for ‘High’.

Before Sadiq Khan became Mayor, social media and text alerts have been used on a small number of occasions to make Londoners aware of air pollution episodes. Sadiq Khan believes it is important that Londoners are fully informed about toxic air quality and since being elected has delivered a comprehensive alert system using bus countdown signs, roadside signs and electronic updates at underground stations, plus social media and text alerts.

Air-quality alerts will be displayed at:

2,500 bus countdown signs and river pier signs across London.
140 road-side dot matrix message signs on the busiest main roads into London, with instructions to switch engines off when stationary to reduce emissions.
Electronic update signs in the entrances of all 270 London Underground stations.
What is the air quality index?

The air quality index is how we communicate about air pollution levels in a simple way. It is numbered 1 to 10 and divided into four bands, low (1) to very high (10). This system was recommended by the government’s Committee on Medical Effects of Air Pollutants (COMEAP).

What is causing this episode?

There has been a marked increase in particulate levels during Sunday evening which have persisted into Monday. This is due to a combination of poorly dispersed local emissions and sustained import of particulates from Germany and France.

Tuesday’s forecast is based on continued poor dispersion of local emissions and sustained import of pollution from the near continent. The air imported on Tuesday is expected to be more polluted than that arriving on Monday as it is bringing pollution from a working weekday rather than the weekend.

Note: even though the borough average is moderate or low, conditions next to busy roads may still be high or very high. Most people are exposed to pollution next to busy roads.

What is the health advice for ‘high’ pollution?

The Government’s Committee on the Medical Effects of Air Pollutants (COMEAP) advises that adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors, and particularly if they experience symptoms. People with asthma may find they need to use their reliever inhaler more often. Older people should also reduce physical exertion. Anyone experiencing discomfort such as sore eyes, cough or sore throat should consider reducing activity, particularly outdoors.

When was the last episode like this?

Episodes of pollution with high concentrations occur a few times per year in London, but very high pollution episodes are rare.

The last recorded high pollution in London was on 25th July 2018

Share this page