London Congestion Zone Has Reduced Air Pollutant Levels by 60%


The London congestion charge zone was first introduced in February 2003 and was done so with the promise that by charging motorists to enter it, the zone would help to lower emissions in the surrounding area and increase the quality of air in central London.

To show the effect of the congestion zone, Select Car Leasing has analysed air quality data from three DEFRA UK monitoring points within the congestion zone before and after the charge was implemented and what effect the introduction of further congestion zones may have on air pollution in the UK.

How Air Quality Has Improved in London’s Congestion Zone Since its introduction in 2003

The average decrease in pollutant levels across all three monitoring sites in London 2019:

  • Carbon Monoxide levels found to be 62% lower than before the congestion charge was introduced (2002).
  • Nitrogen Dioxide levels also decreased by 24%.
  • Sulphur Dioxide levels decreased by 60%.

Carbon monoxide levels dropped across all three monitoring sites as soon as the congestion charge was introduced.  Carbon monoxide is both odourless and colourless and is caused by an incomplete combustion process which can be extremely harmful to humans. The chemical has been shown cause irritations such as headaches and respiratory problems.

Sulphur dioxide levels in Marylebone have fallen by 62% and 75% in Bloomsbury. Sulphur dioxide is a contaminate caused by combustion engines when sulphur reacts in the atmosphere to form fine particles and other pollutants. This can cause a major health risk, particularly to children.

Nitrogen dioxide has seen a less dramatic fall. Indeed, levels in Marylebone rose in the years immediately after the congestion charge introduction. But then have since fallen dramatically. Nitrogen dioxide causes issues by inflaming the lining of the lungs and reducing immunity to lung infections. Which can then cause problems such as wheezing, coughing, colds, flu and bronchitis.