Pollution in London Underground 30 Times Higher Than Busy Roads: Report
Mon, August 15, 2022

Pollution in London Underground 30 Times Higher Than Busy Roads: Report



From a glimpse, London’s air appears clear. The truth is, the city has suffered from illegal levels of air pollution since 2010. In 2017, reports revealed that London saw its first breach of annual pollution limits just five days into the new year, while in 2018, it occurred within a month. Particularly dangerous levels of nitrogen dioxide, which comes mainly from diesel vehicles, were detected. This means that millions of people in London are living in areas with toxic air. 


Air Pollution in London

2015 data from the Aerosol and Air Quality Research revealed that London was among the most polluted cities in the world, with the highest nitrogen dioxide levels (44.6), next to Paris (48.3), Delhi (49.8), and Beijing (50). London was followed by Madrid (41.2) and New York City (17.6). According to Financial Times, road works, private hire vehicles, and online delivery vans have all contributed to the congestion problem, which results in higher levels of air pollution. 

While the total number of vehicles entering central London has fallen by about 30% since the congestion charge was introduced, the number of private hire vehicles entering central London has more than quadrupled over the same period. “The medieval road system, if you look at the layout and the size of the roads, they were originally designed for horse and cart,” Ruth Calderwood, City of London air quality manager, said.

According to a 2017 study, car drivers in London are causing the most pollution per commuter. It is estimated that around 9,400 Londoners die every year due to poor air quality, costing the economy £3.7 billion. At the same time, air pollution causes 40,000 early deaths in the UK from lung and heart disease. It is also being linked to an increasing range of health impacts, from miscarriage to teenage psychosis. Thus, Prof. Frank Kelly at King’s College London said that the city needs effective measures to improve air quality to an acceptable level.



Fortunately, recent studies show that strict lockdown policies in London have resulted in reduced vehicle emissions. This has caused nitrogen dioxide levels to drop in cities and regions affected by the outbreak. An analysis by the National Centre for Atmospheric Science (NCAS) said that the dramatic reduction in travels has helped contribute to improved air quality across Europe and Asia. 


Pollution in London Underground

If you think London’s streets are polluted, wait until you go underground.

A 2019 study commissioned by Transport for London revealed that the air in London Underground is thick with harmful particulates. The researchers said that some of London’s Tube stations registered levels of air up to 30 times worse than the average for a London street above ground. While no other studies of fine particles on the London Underground were conducted before, the team suggested that it’s possible that particulate pollution of this type is a feature of subway systems across the world.

According to Phys.org, an internet news portal that provides the latest news on science, the researchers wore special backpacks fitted with devices that measure PM2.5 levels during their different testing campaigns to monitor pollution levels in the subway. They compared the variations in PM2.5 levels underground to those above ground in congested diesel areas (Oxford Street) or parkland (Hyde Park), compared across most of the underground network, and analyzed the physical and chemical characteristics of PM2.5 on the southbound platform at Hampstead Northern Line station.

"Our aim in this study was to make high-quality measurements of the PM2.5 that people are exposed to in the London Underground,” lead author Dr. David Green, Senior Research Fellow in the School of Population Health & Environmental Sciences at King's College London, said. 

The findings revealed that the Northern Line had the highest concentration of PM2.5 (tiny particles linked to health problems) with the air on platforms at Hampstead station. The team recorded an average of 492 micrograms per cubic meter (μg/m3) of air, which was a lot higher to the annual average of 16 μg/m3 from a roadside monitoring site in the capital. The concentrations also varied between lines and locations. The Victoria Line, for instance, experienced the highest levels, while Docklands Light Railway and the District Line have the lowest on parts of the lines.

The researchers also found out that passengers are exposed to the same concentration of particulates in an hour on the London Underground as they are during a full day above ground in ambient London air. However, Kelly said that people should still use the trains since there’s of lack of evidence of its harmful effects.



According to Independent, a British online publisher of news, this study is the first comprehensive paper on PM2.5 levels on the London Underground. “The results show that they can be some of the highest concentrations they will encounter during their day. Currently, our understanding of the health effects of air pollution is based on measurements taken by fixed measurement stations above ground. Clearly, these don't represent what people are exposed to as they travel on the underground and these new measurements will help us improve these assessments,” Green said. 

The study revealed two facts: London Underground’s particulate problem is notably worse than other city systems and many harmful particulate emissions on the network do not come directly from fuel combustion. Unfortunately, particulate pollution is also harmful to our health. The researchers revealed that it can cause adverse health impacts including heart disease, stroke, lung cancer, and chronic obstructive pulmonary disease. There’s still not enough research about the relative toxicity of PM2.5 in subway environments and above-ground remains.

“We’ve got all this information about the health impacts of the particles above the surface. Below ground, we know we have a higher mass but of a different type – we don’t yet have the research into the level of the toxicity, and hence the health risk,” Kelly said. 

Lilli Matson, TfL’s chief safety, health and environment officer, added that particulates found underground are very different from those found on the surface. Particulates underground consist predominantly of iron oxide rather than traffic pollutants. Particulates found in the air-ground, on the other hand, are known to be carcinogens. Matson said that there will be further research to gain a better understanding of this. 

“We spend around £60m every year cleaning our trains, stations, and tunnel and are committed to maintaining the cleanest air possible for our staff and customers,” she said.