Concentrations of NO2 have lowered as much as 55% due to less road traffic. However, levels of PM10 and PM2.5 were higher after lockdown than at any other time in 2020, due to easterly winds and pollutants from northern Europe.
Our early analysis of the lockdown showed significant reductions in nitrogen dioxide (NO2) particularly near busy roads in London where in some central areas concentrations were halved. However, the lockdown period coincided with easterly winds and higher temperatures, so we saw increased particle concentrations (PM2.5) as pollutants from northern Europe added to UK emissions to give higher than usual PM2.5 levels. The higher temperatures post lockdown also led to higher ozone concentrations.– Professor Martin Williams, Head of Science Policy and Epidemiology team, School of Population Health and Environmental Sciences, at King’s
Levels of NO2 concentrations, which is released by car exhausts, in busy roadside sites Marylebone Road and Euston Road were down 55% and 36% respectively. The mean reduction in hourly NO2 concentrations lowered by 21.5% across the capital.
However, the research also noted that changes to indoor activity saw some groups of people, such as children and tube users, exposed to a higher level of PM2.5 because of additional time spent cooking at home. This is because particles of pollutants from gas hobs and roasting meats and vegetables. Wood burning also contributed to PM concentrations before and during lockdown, with the evening peak occurring later in the day, reflecting longer daylight hours.
In normal circumstances, the decrease of NO2 concentrations would be beneficial, but these improvements will have been masked by the increased PM2.5 and ozone concentrations. It also remains to be seen how air pollution affects those with COVID-19. More research is needed to assess how air pollution affects health during lockdown and the role of air pollutants in the spread of the virus.– Professor Martin Williams
He continued: "The high concentrations of PM during lockdown is a clear warning that if the UK is to achieve the current WHO PM2.5 guideline then as well as actions in the UK, other European countries will need to achieve their emission reduction targets.”