Changes in UK air quality during the 1st COVID-19 lockdown

The first Covid-19 lockdown led to a 42% decrease in surface-level nitrogen dioxide (NO2) pollution, according to a new study recently accepted for publication in Atmospheric Chemistry & Physics (ACP).

The COVID-19 lockdowns have resulted in stark changes in air quality across the globe and the UK is no exception to this.

Whilst many publications have employed complex modelling or machine learning techniques for analysis, the
researchers adopted a more simplistic approach by comparing air quality during the lockdown period in
2020 to the average over the previous 5 years.

Data from 150 monitoring sites were analysed, showing a 42% decrease in surface NO2 levels across the whole of the UK.

Larger decreases of up to 48% were reported for roadside locations since road transport is the dominant source of NO2.

However, not all pollutants were found to decrease during the lockdown period.

An emerging trend in the air quality data shows that decreases in NO2 were accompanied by increases in Ozone (O3). This study reported an increase in O3 of 11% across the UK.

Strict air quality limits exist in the UK meaning pollutants must remain below a threshold value for compliance. The study showed that whilst there has been a decrease in the number of exceedances of NO2 across all London sites, this has been somewhat offset by an increase in O3 exceedances.

The researchers highlight that this could have interesting implications on air quality in the future, where NO2 pollution from vehicles is expected to decrease as electric vehicles become increasingly popular.

The COVID-19 lockdowns have provided a unique opportunity to study the impact of largely reduced transport emissions, with the decrease in NO2 clearly observed.

However, the concurrent increase in O3 shows its potential to become a pollutant of increasing concern and demonstrates the need for a detailed understanding of the atmospheric processes at work. 

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