The following charts show how the annual average concentration of NO2 and PM10 have changed since 2009 at AURN reference stations in the Borough of Brent.  The trend in NO2 is unclear but probably downwards.  In contrast, concentrations of PM10 are clearly rising.

Source: based on londonair.org.uk  (data for 2025 provisional)

Source: based on londonair.org.uk  (data for 2025 provisional)

Source: based on londonair.org.uk  (data for 20245 provisional)

The following three charts illustrate trends in average annual concentrations of NO2 measured with diffusion tubes around the borough.  Concentrations at most sites shown on the uppermost and lowermost charts have tended to increase since the beginning of this decade.  Prior to 2018, the trend at sites shown on the middle chart was unclear or rising.  Data for 2018 is missing.  Reasons for the substantial apparent improvement between 2017 and 2019 are unclear.

Source:  based on Borough of Brent

The following chart compares trends for successive periods of 12 months) in data reported  by reference monitors and Breathe London nodes in Brent.

 

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