Study: NO2 falls ‘significantly’ in London during lockdown, but PM rises

Levels of NO2 have more than halved in some parts of central London during the coronavirus lockdown, King’s College London scientists have found. However, levels of PM10 and PM2.5 increased due to easterly winds, pollutants from northern Europe and more time spent cooking indoors.

The 40-page document, which is available to read here, analyses various air pollutants monitored by the university’s London Air Quality Network. It has been sent to Defra in response to their call for evidence the research and air quality communities to address the ongoing changes in UK air quality due to the coronavirus crisis.

60% less traffic in the central area is credited with the massive drop in NO2 levels. Reductions in average NO2 concentrations at two busy roadside sites (Marylebone Road and Euston Road) were 55% and 36% respectively.

Overall, the mean reduction in hourly NO2 concentrations was 21.5% across the London roads.

The research 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 and using gas hobs and ovens for roasting meat and vegetables.

They also said wood-burning contributed to PM concentrations before and during lockdown, with the evening peak occurring later in the day, reflecting longer daylight hours.

Professor Martin Williams said: ‘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.

‘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.’