During the first 2020 nationwide lockdown in the UK, there was a surge in press around the noticeable improvement in London’s air quality (The Guardian). An issue that is often elusive to the naked eye became clearly visible for a short period. Lockdown provided a vision of what could be. In credit to London, data recently published by City Hall has shown a dramatic improvement in air quality since 2016, even excluding the effect of lockdown. Despite this progress, it may surprise some to learn that 99 per cent of London does not meet WHO recommended air quality limits and air pollution continues to be one of the most significant issues afflicting the city (London Assembly).

Particulate matter

Within the context of London, there are two main contributors to air pollution – nitrogen dioxide (NO2) and particulate matter (PM2.5). PM2.5 refers to particles that are smaller than 2.5 microns in diameter, that is, 100 times smaller than the width of a human hair. These particles are particularly dangerous because they can penetrate deep into your lungs and even enter the bloodstream. Over recent decades, our understanding of the impact of air pollution on human health has improved significantly. Research has shown that poor air quality stunts the growth of children’s lungs and worsens chronic illnesses, such as asthma, lung and heart disease. More recently, it is emerging that compromising lungs in this manner likely makes it easier for COVID-19 to spread and increases the risk of developing a serious illness from the virus (Science Direct).

Emission sources

So where does it come from? Within cities, the majority of NO2 and particulate emissions come from the transport sector (DEFRA). The most commonly publicised source is tailpipe emissions, particularly those of older diesel vehicles. Modern internal combustion vehicles have come a long way thanks to increased regulation and ever more investment in expensive after-treatment technology. Did you know that modern diesel vehicles inject urea into exhaust gas to reduce NO2 emissions?

With improving tailpipe emissions and the further adoption of electric vehicles, public focus has been somewhat misdirected. According to a Kings College London study, only 7% of PM2.5 pollution comes from tailpipe exhaust fumes (KCL). Tyre pollution and brake dust as emission sources have long evaded public debate. Recently this topic has gained traction thanks to our good friends at The Tyre Collective. Tyres wear out from friction every time we brake, accelerate or turn a corner and the particles become airborne as a result. Tyre pollution is the second-largest microplastic pollutant in our ocean after single-use plastic and accounts for up to 50% of air particulate emissions from road transport, brake dust on the other hand accounts for 20%.

Bicycles and e-bikes

Advocates of battery electric vehicles (BEVs), that is, cars powered by electricity, often describe them as a solution to many urban pollution issues. Hopefully by now the reader can understand that BEVs, in their current form, are not a panacea as tyre pollution and brake dust are independent of powertrain, although brake dust does diminish to an extent with BEVs. Approaching this with an engineering mindset, these are problems humanity has created for itself and they are problems it can engineer out of. There will be car-like vehicles which have zero emissions but be under no illusion, this will take time. More importantly, it will take effort from innovative companies like The Tyre Collective.

In the short term, one of the fastest actions London can take to improve air quality is to migrate travel away from cars and towards bicycles and e-bikes. As an individual who is passionate about cars, I’m not here to vilify car usage. Bicycles and e-bikes emit orders of magnitude less particulate matter than their car counterparts as there is substantially less energy involved when decelerating a cyclist than a 2.5-tonne car.

If we want to improve the air quality of our cities, we need to migrate away from cars to other forms of transport. Cycling and active travel in general form part of the solution.

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