We know pollutants are bad for our health.
But where do London’s emissions originate, and how much of them can we control?

To get a closer look at how pollutants are dirtying our air, we need to consider the sources of pollution in London.

A significant portion of London’s emissions comes from transport – or how we move in, out of and around the city. This includes aviation, river, rail and especially on-road transportation. Construction and industrial processes, as well as heating and powering our homes and businesses, also produce substantial amounts of pollution. Some miscellaneous sources – like accidental fires, agriculture, and forestry – account for a small number of emissions in the city.

Road transport

Some of the most harmful air pollutants – including nitrogen oxides (NOX) and particulate matter (PM) – come from on-road vehicles, including cars, lorries and buses. Breathe London’s monitoring network measures the key pollutants that combine to form NOx (NO₂ and NO), as well as two of the most detrimental forms of PM (PM₁₀ and PM₂.₅).

The fuel used to power our vehicles is critical. Diesel is an especially harmful polluter, responsible for almost 50 percent of all road transport NOX emissions and a main source of PM emissions in London. Research by Oxford University reveals that the health damage effects associated with diesel vehicle emissions are at least 5 times more than those associated with petrol vehicles and around 20 times more than electric vehicles.

Industrial and commercial

Another main contributor of pollution in London is the industrial and commercial category. This includes a wide range of activities like sewage treatment and construction, as well as some heat and power generation. As noted in the charts above, industrial and commercial sites are major sources of local PM pollution, largely because of dust and emissions from machinery.

Targeted solutions

Air quality in London is a multi-pollutant problem. Numerous pollutants from numerous activities create a toxic soup, which is made worse by different weather conditions. And a few sources of emissions are difficult or impossible to control or reduce. For example, PM comes from many natural sources, such as sea salt, forest fires and Saharan dust.

The good news is, many pollution sources – like road transport and most industrial processes – are both manmade and controllable. Switching to electric vehicles, for example, virtually eliminates direct fossil-fuel combustion emissions from cars.

Focusing on the sources that we can control provides a huge opportunity to reduce pollution, especially since acting on a single source can address multiple pollutants. For example, lowering emissions from road transport lowers NOX and PM as well as secondary pollutants like ozone.

Largely a manmade problem, ozone is formed predominantly from the interaction of other pollutants like NOx, volatile organic compounds (VOCs) and methane. VOCs are released from burning fuel such as gasoline, wood, coal or natural gas. Methane is emitted through a range of manmade activities including oil and gas and agriculture.

Through the stationary and mobile monitoring network, Breathe London aims to determine the sources of pollutants on a granular level. We’ll do this by measuring carbon dioxide (CO2), an important marker, alongside the other air pollutants. By studying the ratios of pollutants to CO2, we can gain insights into what is causing the pollution. This data can then inform smarter policies and approaches to building healthier communities.

The information on this page comes from the 2016 London Atmospheric Emissions Inventory (LAEI), which catalogues London’s emissions by source and location. The LAEI covers the 33 London Boroughs, the City of London, and the geographic area of Greater London.

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