The UK-wide coronavirus lockdown led to a drop in nitrogen dioxide levels, with the air pollutant reaching low concentrations not seen in the past decade.
Jonathan Higham at the University of Liverpool, UK, and his colleagues analysed data from the UK government鈥檚 Automatic Urban and Rural Network between the start of the lockdown on 23 March through to 28 April.
The network comprises 300 sensors distributed around the UK. Each hour, they collect information including the levels of nitrogen dioxide and sulphur dioxide, along with measures of tiny particulate matter known as PM2.5 and PM10. All are potentially harmful to human health.
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On average, and sulphur dioxide levels in the UK have been decreasing for the past decade. The team found that during part of the lockdown period, the average daily UK concentration of nitrogen dioxide dropped to less than 5 micrograms per cubic metre.
The findings are in keeping with satellite data that has previously found in atmospheric nitrogen dioxide over parts of and , coinciding with lockdown measures.
Nitrogen dioxide has been linked to respiratory and cardiovascular problems. In 2018, approximately 3 million tonnes of nitrogen dioxide were produced in the UK, 30 per cent of which came from road traffic.
The team also found that lockdown measures had no significant impact on the levels of PM2.5 and PM10 in the UK, and that the production of sulphur dioxide actually increased to a five-year high. The reason for the rise is still unclear, says Higham.
Sulphur dioxide gas, much of which is produced by domestic heating and coal-fuelled power stations, can also be created from ozone in the atmosphere, which is in turn influenced by humidity. As such, the UK鈥檚 unusually dry weather听over the past several months may be a factor, says Higham.
The team has already begun to see a rise in nitrogen dioxide levels as people return to driving again. 听鈥淚 think it鈥檚 quite evident that they鈥檙e just going to go back to normal levels,鈥� says Higham.
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