Is the cold snap to blame for London’s ‘high’ air pollution alert?

Londoners have been asked to avoid unnecessary car journeys after high air pollution alert issued

Is the cold weather fuelling London’s air pollution?

On Monday, London Mayor Sadiq Khan issued a high air pollution alert for the capital – the warning follows the moderate air pollution London has been experiencing since Saturday as temperatures plummeted.

Sadiq Khan said: “I am urging Londoners to look after each other by choosing to walk, cycle or take public transport where possible, avoiding unnecessary car journeys, stopping engine idling and not burning garden waste, all of which contributes to high levels of air pollution.”

Speaking to Evening Standard’s The Leader podcast, Frank Kelly, Professor of Community Health and Policy and Head of the Environmental Research Group at Imperial College London said: “There were a couple of reasons for the pollution to get worse in London in the last few days, the primary reason has been this very cold air event that we have been having.

“So we have had this blanket of cold air across London and parts of England and that has acted as a trap for all the pollution that’s being emitted from different sources on the ground, from vehicles, from domestic wood burning or fires.

“The way we think about this is to think of boiling a pot of water and if you don’t have the lid of the pot, then the steam gently escapes. But if you put the lid on the pot of water, then the steam hasn’t got anywhere to go and the pressure builds up.

“And that’s exactly what happens when we’ve got this cold inversion across the South of England.”

Professor Kelly added that one more reason behind the increase in London’s air pollution is the increase in demand for heating amid the cold snap. He said: “That in many cases could be open fires or wood burners”.

Asked whether this type of alert is common, Professor Kelly replied: “They are not very frequent at all. If we think about over the last five or six years, on average it’s maybe only, only two or three times a year. If it’s an exceptional year we might see five or six high alerts.”

Air pollution across London is monitored every day and is reported on the website London Air. Using government guidance, the air quality is rated on a scale of one to ten. When the air quality is between one and three, this is low air pollution event, when it’s between four and six, is a moderate air pollution event, from six to nine is high and whenever it’s ten it’s very high.

On Monday and Tuesday, London experienced high pollution events in certain areas.

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