AIR QUALITY MATTERS

City of London
Low-hanging fruit gone?  Resting on laurels?  Promoting CO2?

 

Reference monitors
The following three charts derive from data measured by reference monitors.  This high quality data is "ratified" up to the end of Q1 2025.  Its sources are  Air Quality England (and London Air).
The charts indicate that concentrations of nitrogen dioxide ("NO2") greatly decreased since towards the end of last decade.  The LEZ, ULEZ and efforts by the City of London will have contributed to the improvements.  Since then, progress seems to have stalled and concentrations exceed the World Health Organisation ("WHO") guideline by a factor of between two and four (perhaps more at Walbrook Wharf).
 Concentrations of particulate matter ("PM10" and "PM2.5") have also decreased, but by rather less.  Those for PM10 now match those of the World Health Organisation ("WHO") guideline for PM10.  Those for PM2.5 are fluctuating around double the WHO guideline at the only site which has been continuously monitored during recent years.  In terms of mass, commercial cooking is understood to be a leading contributor to PM2.5 in the City of London. However, particle number not mass is more salient to health.  

 

The following three charts illustrate how concentrations of NO2, PM10 and PM2.5 - at each hour of the day - varied on average during the 12 months 01 October 2024 to 30 September 2025.  The charts contrast working weekdays with weekends & public hoildays.



Diffusion tubes
The following charts show how the annual average concentration of NO2 has changed since the second half of last decade at sites being monitored long-term using difusion tubes in the City of London.  The tables between the charts indicate the location of the sites shown by (the local authority's) code numbers.  This information derives from the local authority's Air Quality Annual Status Reports

The data shown includes estimates where the source data is either missing or likely to be erroneous.  The data shown is "raw" - it has not been "adjusted for bias".  12-monthly average concentrations have declined substantially since early 2020.  However, after adjusting for bias (by multiplying raw data by between 0.8 and 0.9), concentrations at a few locations approximate to the UK legal limit - as indicated on the charts below.  That limit is four times greater than the World Health Organisation guideline (which is based on seveal more recent years of evidence and research). . The recent trend is - at most locations - slowly towards lower concentrations.
That said, from the air quality point of view, the city is still not a good place to be out of doors.  However, it may be better than in the central business districts of most other capital cities.  What about indoors?

 

 

 




 Nitrogen dioxide emissions tend to be associated with combustion - along with carbon dioxide.  The lack of progress since the climate emergency was recognised reflects that progress towards Net Zero is lagging well behind where it should be (- government is not heading the warnings of the Committee on Climate Change).  Delay is not negotiable.

The following chart does not take into account (i) greenhouse gas emissions associated with projects, businesses, etc. outside the City of London which receive services from businesses in the City - likely to be huge - or (ii) travelling to the City.  The chart indicates that the great majority of the City's emissions derive from electricity and gas.  Emissions from gas are tending to increase as LNG displaces "natural" gas.  As with wood pellets (and wood-based biogenic waste), emissions associated with production of LNG are large but ignored simply because they occur outside UK jurisdiction.  The energy generated by burning those fuels is not low-carbon / clean / decarbonised.
The source of the chart's data was published 18 months after the end of the most recent year shown - despite an obvious need to audit progress at intervals of at most six months given the Climate Emergency.  The GLA tends to release the data to London local authorities six months after they are published.
For further information, please contact:
 info@airqualitymatters.uk
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