Why Is London's Air So Bad Right Now?

Pollution in the UK capital reached alarming levels at the beginning of this month, as concentrations of particulate matter 2.5 (PM2.5) and nitrogen dioxide (NO2) reached over double the normal amounts.

As a result, Londoners were encouraged to leave their passenger cars at home on Monday 5^th December and to avoid strenuous outdoor activity if at all possible. Special attention was also advised when taking young children outdoors, since their underdeveloped respiratory systems are at particular risk from the contaminants.

The diesel dilemma

London has struggled with worrying levels of pollution over the last 10 years or so, largely due to the proliferation of diesel vehicles within the city limits. The government had initially encouraged car owners to switch from petrol to diesel due to the reduced amounts of carbon dioxide (CO2) that diesel engines emit.

However, it later surfaced that while diesel engines do produce less CO2, they produce significantly more NO2 and PM2.5, themselves two damaging contaminants. The latter is of particular concern due to its diminutive size. With a diameter of no more than 0.0025mm, these particles can easily be inhaled and even absorbed into the bloodstream, causing no end of respiratory and cardiovascular complications.

In order to gain a better understanding of the problem, mobile monitoring stations have been used to assess diesel emissions in places like Greece. Similar monitoring equipment is also employed in the UK capital by the London Air Quality Network, who found that pollution levels were as high as nine or ten earlier this month. Normally they hover between one and three.

Tis the season

The reason for the exacerbated pollution conditions right now is down to a combination of factors. Firstly, the cold snaps that are invariably brought on by the onset of winter create a layer of colder air at ground level. This acts as a blanket, effectively trapping contaminants and creating a dirty layer of smog over the city.

Secondly, the lack of wind has meant that this smog has not dissipated easily, while the largely dry weather has not allowed rain to clear away the smog, either.

Finally, polluted air has also been wafting over the English Channel from France, as well. The French capital of Paris has endured similarly poor air quality as London over the last decade or so and this has led to elevated levels of pollution over the city at the start of the month.

More action required

London Mayor Sadiq Khan has responded to the recent air quality crisis by asking people to leave their vehicles at home, in a similar move to one practiced in Paris last September. However, some critics have questioned whether measures like these really go far enough in addressing the root cause of the problem.

“It’s great the Mayor has issued air pollution warnings but these don’t go far enough, you need to tackle pollution at its source not just tell people that it’s happening,” said Caroline Russell, a member of the Green Party. “I have supported the Mayor’s idea for Paris-style ‘car-free’ days, but car-free days are no substitute for decisive action on air pollution and traffic reduction.”

Meanwhile, the Mayor’s office has defended his policies, claiming he is doing all that he can to clean up the capital’s airwaves and calling on the Conservatives to help.

“The Mayor is transforming London’s buses into one of the greenest fleets in the world and last week announced no more pure diesel buses will be procured from 2018,” a spokesperson commented. “The Mayor is doing everything in his power to tackle London’s toxic air and get rid of the most polluting vehicles, but he cannot do this alone and is calling on the Government to face its responsibility and implement a national diesel scrappage scheme now.”