The following thee charts show how the annual average concentration of NO2, PM10 and PM2.5 have changed since 2009 at AURN reference stations in the Borough of Brent.  The current trend in NO2 is unclear but probably downwards.  That for PM10 is unclear.  For PM2.5 it is upwards (caused by what - factors in Brent? in London? outside UK? climate change?).  If the number (also shape and chemical composition) of particles per unit of volume determines health impact, then trends in weight per unit of volume might be misleading.

Source (for the three charts above): based on londonair.org.uk  (data for most of 2025 is provisional)

The following three charts illustrate trends in average annual concentrations of NO2 - "ratified and bias-adjusted" - as measured using diffusion tubes around the borough.  The 50% improvement since 2017 is presumably at least partly attributable to the ULEZ. 

Source:  based on Borough of Brent

 

Trends in NO2 concentration measured by HS2 using diffusion tubes are shown below.

 

The following chart indiates that, since Brent, the GLA and UK recognised the Climate Emergency, borough-wide progress towards decarbonisation lags far behind the (more than) 10% each year which is now imperative.  Borough-wide emissions during 2024 or 2025 are unlikely to be lower than they were during the 2022/2023 energy crisis. The global carbon budget for "well below 2C" is likely to be exhausted before 2050 - even sooner for the UK's share (necesarily apportioned according to the country's legacy and wealth) of this.

Source:  based on DEFRA