The following charts illustrate changes in the annual average concentration of three air pollutants which have occured since 2012.  The measurements reflect conditions in the immediate vicinity of the monitoring site rather than in the named locality.  The measurements for 2022 have yet to be fully ratified.  They are based on London Air.

 

Indicative (implicitly unratified) concentrations of nitrogen dioxide ("NO2") and fine particulate matter ("PM2.5") are being measured at several locations across London through Breathe London, including in this borough.   Four are co-located with reference monitors.  This helps calibrate other indicative devices managed by Breathe London.  The following chart compares trends between concentrations reported for reference monitors which are co-located with indicative devices and diffustion tubes.  The latter has not been adjusted for bias.  The difference between the concentrations reported for the reference monitors and the diffusion tubes indicates the annualised "bias adjustment factor" which one might apply to NO2 diffusion tubes located elsewhere across the borough (but DEFRA rules constrain the bias adjustment factors which local authorities adopt).

 

The following four charts illustrate trends in nitrogen dioxide concentrations as measured since 2014 using diffusion tubes across Greenwich.  Concentrations at all the locations would be lower than the current legal limit - once adjusted for bias (see above) - typically by multiplying by between about 0.7 and 0.9 (as indicated in the chart above).  The data, based on Royal Borough of Greenwich, have not been adjustment for bias.  Estimates have been made for March to June 2020 inclusive (when covid-19 restrictions were in place) and other months if data is missing or spurious.  The uppermost chart refers to sites where triplicate measurements were made (- see previous paragraph).