Click chart for full time series	Click chart for full time series
Monthly trends
	Groups of sites: Abbey Road to Maida Vale Finchley Road - Wellington Road Central sites Schools Avenue Road and neighbourhood
Click chart for each group of sites	Click a name to open chart for the given group of sites

Trends in annual averages

	Groups of sites: Abbey Road to Maida Vale Finchley Road - Wellington Road Central sites Schools Avenue Road and neighbourhood
Click chart for each group of sites	Click a name to open chart for the given group of sites

Supplementary charts

Indicative average concentrations of NO2 and PM2.5 - and their variation throughout the day (as measured using EarthSense Zephyrs, funded by Westminster City Council)

Arnold House
Barrow Hill Junior School

Trends in average NO2 concentrations for successive periods of 12 months
Source: Air Quality England (or London Air)  (* busy roadside, ** quiet, background site)
Remarks:  Introduction and extension of the Low and Ultra Low emission zones explains much of the reduction in air pollution from NO2 which occured during periods of a year or so either side of official covid-related constraints.  The rate of improvement since then has been slow, implying that further intervention is required - the current UK limit 40 µg/m³ is four times greater than the World Health Organisation guideline.


Diurnal variation in average ratified NO2 concentrations - 01/06/2024 to 31/05/2025
Source: Air Quality England (or London Air) (* busy roadside, ** quiet, background site)
Remarks:  Weekday concentrations exceed those on days off, have a more pronounced morning rush hour peak and an earlier evening peak.  The lowest concentrations - best for outdoor exercise - tend to be at lunch time (and 3 am).  Data for Wicken Fen (Cambridgeshire) is included for contrast.


Diurnal variation in average ratified PM2.5 concentrations - 01/06/2024to 31/05/2025
Source: Air Quality England  (or London Air) (* busy roadside, ** quiet, background site)
Remarks:  Concentrations of PM2.5 tend to vary little not only between the working week and days off, but also with time of day.  They exceed the World Health Organisation guideline by a substantial margin.  Data for Wicken Fen (Cambridgeshire) is included for contrast.


Trends in average PM2.5 concentrations for successive periods of 12 months
Source: Air Quality England (or London Air)  (* quiet, background site)
Remarks:  Declining concentration of PM2.5 prior to 2023 are at least partly attributable to Low and Ultra Low Emissions Zones prior to and since covid lockdowns.  The dip between 2023 and 2024 and the subsequent increase may be attributable to fluctuating meteorological conditions (direction & strength of the wind), exacerbated by climate change.   Agriculture, constuction and industry - not just in the UK - contribute to PM2.5 concentrations in London.