March 24, 2020

expert reaction to drop in air pollution because of COVID-19

There have been reports of reduced air pollution levels around the world, due to reduction in activity from COVID-19 responses.

Dr Eiko Nemitz, Environmental Physicist at the UK Centre for Ecology & Hydrology (UKCEH), said:

“The reduction in traffic and industrial activity caused by COVID-19 has already led to the observation of reductions in some air pollutants across the UK, such as nitrogen dioxide, from space.

“However, it is likely that there will not be a reduction in all pollutants. As more people stay at home, some domestic emissions may go up in some residential areas, for example, particulate emissions from woodstoves as long as outside temperatures remain cool.

“In spring, agriculture typically makes a substantial contribution to particulate matter pollution across the UK, due to the emission of ammonia from livestock wastes and fertilised fields. With agricultural production continuing, this source of pollution is likely to be much less affected by the COVID-19 situation.

“UKCEH’s measuring stations across the country will monitor the impact on ammonia pollution, while our carbon dioxide emission measurements on the BT Tower are uniquely placed to track changes in fossil fuel use in central London.”

Professor Hugh Coe, Director of the Manchester Environmental Research Institute,  University of Manchester

“The lockdown of the UK in response to the increasing risk of coronavirus is having a dramatic impact on the level of pollution in cities across the UK.  Nitrogen dioxide and particular matter levels have reduced considerably over the last week compared to typical concentrations at this time of year, mainly as a result of reduction in traffic.  These data are showing us what may happen in the future as transport shifts to an electric fleet.  Nevertheless, electric vehicles won’t cut emissions of particulate from non-exhaust sources such as brake and tyre wear which will need improved public transport infrastructure to reduce the reliance on private vehicle use.”

Prof William Collins, Professor of Meteorology, University of Reading, said:

“A large amount of the air pollution we breathe comes from traffic. With many countries on lockdown the levels of traffic pollution have plummeted. Satellites have picked up very large decreases in levels of NO2 (primary from diesels) in all industrial regions of the world. We expect fine particulate matter (PM) has similarly reduced. Big reductions exposure to pollutants will also have come because people are no longer walking on the streets. It is too early to say whether these improvements will offset any of the mortality from Covid-19, or other health problems due to be confined indoors.”

Prof Anna Hansell, Professor in Environmental Epidemiology at the University of Leicester, said:

“There are an estimated 40,000 deaths in the UK per year due to outdoor air pollution (Royal College of Physicians report figures) and 4 million deaths worldwide (WHO figures). The Committee on Medical Effects of Air Pollutants have reviewed evidence on PM2.5 (fine particulates) and NO2 in the past two years. It found that each annual average 10 microgram/m3 increase in PM2.5 (fine particulates) is associated with an increase of 6% in mortality and each 10 microgram/m3 increase in annual average NO2 with an increase of 2.3% in mortality.  

“Air pollution will fall dramatically in line with travel restrictions and reduction in industrial emissions – we have seen that already in Wuhan in China (one of the most polluted cities in one of the most polluted countries) and northern Italy (one of the most polluted areas in Europe). 

“Sadly we may not see reductions in air pollution translated into direct drops in mortality. In fact, it will be very difficult to interpret mortality trends in 2020-2021 – there will be an increase in numbers of deaths due to COVID-19 but also impacts of financial hardship and stress (we know that poverty increases risk and severity of chronic diseases and also death rates), adverse impacts of isolation of the elderly (impacting on their health in various ways) and impact of restrictions on access to healthcare for non-COVID-19 diseases. The latter three are likely to have knock-on effects on mortality for several years after the pandemic. On the plus side there should be reduced transmission of various infections at least in 2020-21 from social distancing, leading to reductions in deaths from infectious disease such as non-COVID-19 pneumonia (currently 25-30,000 deaths per year in England).

“It is interesting to speculate whether air pollution in Wuhan and Italy areas may have had an impact on susceptibility to the virus, either directly affecting infection rates or indirectly affecting severity (via contributions to increased heart and lung disease that put you at greater risk of severe COVID-19 disease) – it’s an area that needs further research.”

Prof Alastair Lewis, Professor of Atmospheric Chemistry, National Centre for Atmospheric Science, University of York, said:

“Air quality has started to improve in many UK cities, mirroring what has been seen in other countries that have restricted travel and levels of outdoor activity.  This is primarily a consequence of lower traffic volumes, and some of the most clear reductions have been in nitrogen dioxide (NO2), which comes primarily from vehicle exhaust. However fine particles (PM2.5) have also reduced significantly.  In London for example PM2.5 is noticeably lower than would be expected for this time of year at the roadside, and these reductions stretch through into the suburbs as well. 

“Since there is no lower threshold for harm for most air pollutants, any improvement in air quality brings real health benefits. In the midst of a respiratory health crisis such as this, better air quality can only have a small effect, but it will undoubtedly be positive, relative to business as usual levels of pollution.  It is further motivation, as if it were needed, to stay inside and not travel unless necessary, since the emissions and pollution avoided makes a helpful difference.  

“The temporary reductions in emissions being seen at the moment provide us with some unique insight into what might be possible for future air quality in cities. The large reductions being seen in transport emissions of NOx allow us to evaluate how the atmosphere will respond to a future electrified fleet that will no longer emit this pollutant. The chemistry of the atmosphere is complex with many contributing sources, and this ‘clean’ period is likely to help in inform what air quality standards might be feasible for secondary pollutants such as PM2.5 and ozone in the future.”

Prof Jonathan Grigg, Professor of Paediatric Respiratory and Environmental Medicine, Queen Mary University of London (QMUL), said:

“During the pandemic, staying indoors and reduced road emissions will protect vulnerable people from the adverse effects of air pollution.  When the pandemic is over it should be possible to assess this using routinely collected NHS data. I hope that after the lock down has ended, we can move into a cleaner breathed environment, and one where we are more aware about protecting vulnerable people from respiratory virus infections.”

All our previous output on COVID-19 can be seen at this weblink: www.sciencemediacentre.org/tag/covid-19/

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