London catches a breath of fresh air

Winter 2022

London catches a breath of fresh air

When Sadiq Khan became mayor, decreasing air pollution was a top priority. Here’s how new policies have reduced health risks.

London made reducing air pollution a priority starting with the election of Mayor Sadiq Khan in 2016. It established low emission bus zones, toxicity charges aimed at older vehicles, and a variety of other measures, all with an eye on improving the health of its residents. Levels of fine particulate matter have been reduced, but the biggest impact in the last four years has been on nitrogen dioxide.

NO2 MoleculeNitrogen dioxide (NO2): A pollutant produced by burning fuel; inhaling it can both cause and exacerbate respiratory illnesses such as asthma.


Average Annual NO2 concentrations

Map depicting average annual NO2 concentrations in 2016, showing high concentrations of NO2 from the center of the city, reducing to safe levels on the edge of the city.


Average Annual NO2 concentrations

Map depicting average annual NO2 concentrations in 2019, showing decreased concentrations of NO2 from the center of the city, reducing more drastically to safe levels from the city center out

Map legend depicting range of colors for NO2 exposure from safe (blue) to danger (orange)

The United Kingdom and the European Union have both set 40 micrograms per cubic meter as their legal limits.

Beyond limits

Annual mean values for NO2 in the atmosphere should not exceed 40 micrograms per cubic meter, according to the World Health Organization.

In addition, spikes of up to 200 micrograms per cubic meter were not to exceed 18 hours a year at any given site.

Map of central london in 2016 showing very high levels of NO2In 2016, 25 sites surpassed this level, totaling more than 4,000 hours above safe thresholds. Most of London was in an acceptable range. Central London was not.

Central london in 2019 showing much better NO2 levels with a white outline showing the part of the city that inside the ULEZ zone.In 2017, London created its first Low Emission Bus Zone and began phasing out diesel-fueled buses and taxis. It also established a Toxicity Charge in Congestion Zones, an extra fee for vehicles not meeting Euro 4 emissions standards.

By 2019, Central London NO2 levels were much improved. And it became home to the city’s first Ultra Low Emission Zone. (white outline)

Reducing NO2 levels is projected to reduce related diseases by 29% by 2050, saving the National Health Service more than 1 billion pounds sterling annually.

Electric busAs of 2019… Only 119,000 Londoners live in areas above the legal limits, a 94% drop. Hourly spikes exceeding safe thresholds dropped 97%, to 114 hours, with Oxford Street in Westminster enjoying the greatest improvement.

On average, 13,500 fewer old vehicles are in the city center every day. All buses in Central London are low emission.

Breathing easier

Overall levels of NO2 in London fell by an average of 21%. And in Central London, they fell by more than 30%.

Putney facadeThe biggest reduction—50%—took place at Putney High Street Façade (indicated at left), where London’s first Low Emission Bus Zone was introduced in 2017.

Changing measures

Mayor KhanDespite making headway, congestion remains a serious issue in London, and Mayor Sadiq Khan recently called on Londoners to drive less.

Map data: City of London.
Projections: Dakota Bailey and Jeff Blossom / Center for Geographic Analysis, Harvard University.
Electric Bus: Jamie Lorriman / Alamy Stock Photo.
Sadiq Khan: Greater London Authority.