Data from sensors on Horseferry Road in Westminster show a significant rise in nitrogen dioxide (NO2) levels on December 11, the day of a farmers’ protest against inheritance tax changes. The protest, involving tractors in central London, led to NO2 concentrations more than three times higher than the World Health Organization’s (WHO) recommended limit.

Two sensors tracked the pollution spike: one from a Department for Environment, Food and Rural Affairs (DEFRA) station and the other from the Imperial College-led Breathe London network. According to the Breathe London data, NO2 levels soared above the WHO target of 25 micrograms per cubic meter, peaking at about 80 micrograms in the afternoon. DEFRA’s sensor also recorded two sharp increases in NO2 around the protest period.

Westminster Council noted that air quality spikes are common due to various factors like traffic or weather. However, internal communications highlighted that these increases could be directly linked to the protest, with no similar spikes observed in the days leading up to it. The sharp rise in pollution underscores concerns about the environmental impact of large-scale demonstrations in busy urban areas.