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Covid-19 UK lockdown saw unexpected rise in air pollutant

The first 100 days of the UK coronavirus lockdown resulted in significant drops in air pollution, specifically nitrogen dioxide (NO2) levels, scientists have found, but sulphur dioxide saw big rises in the same period.

A study from the University of Liverpool has found that NO2 levels were cut by half due to drastically decreased traffic on the roads while levels of sulphur dioxide increased by over 100 per cent.

When assessing the period from 23 March to 13 June 2020 using air-quality sensors and UK Met Office data, the falls in NO2 were anticipated, but levels of sulphur dioxide, which is typically created by UK industry but in sharp decline, were more than double that of previous years.

The team looked at the localised effects of lockdown on air quality in seven large UK cities: London, Glasgow, Belfast, Birmingham, Manchester, Newcastle and Liverpool.

This revealed that NO2 levels in all of the cities reduced on average between 37 and 41 per cent, with only Glasgow seeing a larger 44 per cent decline. However, northern cities were found to experience greater increases in sulphur dioxide.

Lockdown in the UK came into effect on 23 March 2020 when Prime Minister Boris Johnson told the country that people ‘must’ stay at home and certain businesses must close.

This resulted in the significant reduction in motor vehicle usage with the first day of lockdown seeing a reduction to 69 per cent of normal. This reached a low of 23 per cent on 13 April before steadily increasing back up to 77 per cent 100 days after the lockdown began. The first 100 days of lockdown also coincided with higher temperature and less humidity.

Lecturer Dr Jonny Higham, who led the study, said: “The results of our analysis are surprising. It is evident that the reduction in motor vehicles and human activity had a substantial impact on air quality as demonstrated by the reduction in nitrogen oxide. However, although it reduced one pollutant there has been a big increase in another pollutant.

“We think these changes could be driven by an in-balance in the complex air chemistry near to the surface exacerbated by the meteorological conditions in particularly low humidity levels and changes in pollutions concentrations.

“It is important to note that the complex and relatively stable air composition in the near surface layer can be disrupted in a short period of time by the significant reduction of primary emissions from human activities. For the case of UK, getting cleaner air from a large NO2 reduction may not be as straightforward as it seems.”

Earlier this month another study suggested that the level of toxic fine particles in Scotland’s air failed to go down during the Covid-19 lockdown.

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