Sadiq Khan issues ‘Very High’ air pollution alert in London

23 January 2017

Responding to the issuing of the first ‘Very High’ air pollution alert since he became Mayor of London, Sadiq Khan said:

“Today the shameful state of London’s toxic air has meant that I am forced to trigger the first ‘very high’ air pollution alert under my new comprehensive alert system.   

“This is the highest level of alert and everyone - from the most vulnerable to the physically fit - may need to take precautions to protect themselves from the filthy air.

“Safeguarding the health of Londoners from pollution is my number one priority – and we are implementing the boldest policies of any city in the world to get to grips with the awful problems we inherited.

“We’re delivering the strongest emission measures  to clean-up our bus fleets, charging for the dirtiest most toxic diesels, and bringing forward and then extending the Ultra Low Emission Zone.

“The government urgently need to do their bit. They need to devolve more powers to London and introduce a national diesel scrappage scheme to rid our streets of the dirtiest vehicles.  They also need to reform vehicle excise duty and bring in a new Clean Air Act that finally tackles this problem and means that Londoners don’t have to be afraid of the air we breathe.”


Notes to editors

This is the first ‘very high’ air quality alert since Sadiq Khan became Mayor – the next step up from the ‘high’ alerts which have been issued over recent weeks.

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 Committee on Medical Effects of Air Pollutants (COMEAP).

What is air pollution currently like?

Current particulate matter pollution levels in London are classified ‘very high’ or 10 out of 10. This means that PM10 concentrations are 101micrograms /m3 or more – roughly more than double the legal hourly limit.

What is causing this episode?

Cold, calm and settled weather is resulting in elevated air pollution levels. Low wind speeds are leading to poor dispersal of local pollutants meaning pollution has built throughout the course of several days.

Today’s conditions are partly being caused by the slow dispersal of emissions from Sunday afternoon/evening where there was an unusually high amount of domestic wood burning. (King’s think that about half the pollution at some sites was coming from domestic wood burning.)


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 ‘very high’ pollution?

The Government’s Committee on the Medical Effects of Air Pollutants (COMEAP) advises adults and children with lung problems, adults with heart problems, and older people, should avoid strenuous physical activity. People with asthma may find they need to use their reliever inhaler more often.

Everyone is advised to reduce physical exertion, particularly outdoors and by busy roads, especially if you experience symptoms such as cough or sore throat. For example, you might want to avoid going for a run today.

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. 

This is the first ‘very high’ alert for 2017. However, in 2016, there a very high episode in March and another serious episode at the end of November/beginning December.