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NO₂ in London

13th February 2017

London has some of the highest levels of street pollution in the world. Oxford Street, a busy shopping zone, is one of London’s most polluted streets. High concentrations of Nitrogen Dioxide (NO2) have been recorded. This pollutant is produced when fossil fuels are burned. Oxford Street is particularly badly affected owing to the volume of traffic on the road.

NO2, as a concentration, is measured in micrograms per cubic metre of air (µg/m³). A concentration of 1 µg/m³ means that one cubic metre of air contains one microgram of Nitrogen Dioxide. In a recent pollution report by Kings College London, Oxford Street is found to have an average amount of 143 micrograms of NO2 per cubic metre. The report also states that there were 1,532 hours during the year when that figure was above 200 micrograms. According to the World Health Organisation, the average level of NO2 should not exceed 200 micrograms more than 18 times a year.

The prevalence of NOis partly attributable to the fact that buses in London are using diesel oxidation catalysts and particle filters. In order to burn off the black soot from diesel engine emissions, exhaust gases need to reach temperatures in excess of 500°C; however, NO2 can be used to burn these sooty particles at a much lower temperature (around 200°C). As a consequence, higher amounts of NO2 are released into the atmosphere.

There are many ways to monitor such pollution in open industrial areas. Munro Instruments offers a device which detects harmful substances in the air. Our Ambient Air Monitoring System provides real-time air quality measurements and sends out alarms and SMS messages to key stakeholders when dangerous limits are breached. This type of monitoring is essential in large, busy cities, as high levels of pollution can cause respiratory problems and inflammation of the lungs. Transport for London (TfL) has now introduced pollution alerts in London, which can be found at bus stops and train stations.

If you would like further information about any of our Air Quality products, please get in touch via email ( or phone (+44 (0) 20 8551 7000).