Lockdown air: less NO2, same PM2.5 and more urban ozone 

#GS3 #AirQuality #Pollution 

In a pandemic whose impact on public health, the economy and the environment is still unfolding, here is a new finding: While traffic pollution has been falling, the lockdown may be leading to the generation of a dangerous pollutant, urban ozone, which can cause airway inflammation in humans. 

  • The research is specific to the UK. It has been conducted by experts from The University of Manchester, led by Hugh Coe, Professor of Atmospheric Composition, plus air pollution expert Dr James Allan from Manchester’s Department of Earth and Environmental Sciences. The findings have been submitted in response to a call for evidence from the UK government’s Department for Environment, Food and Rural Affairs (Defra), the university said in a statement. 

Nitrogen oxides:  

  • Levels of nitrogen oxides were found reduced in most locations in the UK during mid-March and April.  
  • The level of decline ranges from 20% to 80 %. Levels of nitrogen oxides fall less in rural areas than urban areas; and they are higher in the morning than compared to later in the day. 


  • There was no evidence of a decrease in PM2.5.  

Urban ozone:  

  • The Manchester team speculated that photochemical production of ozone may become more important in urban areas during summertime in these low conditions of oxides of nitrogen.  
  • As nitrogen oxides reduce, photochemical production may become more efficient and can lead to higher ozone concentrations in the summertime as higher temperatures increase emissions of biogenic hydrocarbon from natural sources such as trees.  
  • These biogenic hydrocarbons significantly affect urban ozone levels. 

While ozone is important for screening harmful solar UV radiation when present higher up in the atmosphere, it can be a dangerous at the Earth’s surface, and can react to destroy or alter many biological molecules.

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