The following chart shows how the annual average concentration of NO2 changed between 2015 and 2017 at a selection of sites in the Borough of Hackney.  Click on the chart in order to view charts of several other sites.

Source:  based on “Air Quality Annual Status Reports" for 2015, 2016 and 2017  Borough of Hackney

The data above indicate that NO2 concentrations exceed the legal limit at all the sites shown, and are not decreasing.

In contrast, data continuously measured in Old Street (shown on the following chart) suggest that air quality there is clearly improving: 

Source of data: London Air (prior to 2021) and Air Quality England (from 2021)

Similarly, data continuously measured with reference monitors (shown on the following chart) suggest that concentrations of particulate matter (PM10 and PM2.5) have also declined - but the recent trend at Old Street is unclear. 

Source of data: London Air (prior to 2021) and Air Quality England (from 2021)