UK MPs told air pollution is likely to be driving Covid-19 infections and mortality

MPs and others attending via video link of the Air Pollution All Party Parliamentary Group (APPG), chaired by Geraint Davies (29 May), took evidence from Rachel Nethery and Xiao Wu of Harvard University on their research into the relationship between air-born particulate matter (PM2.5) and deaths from Covid-19.

The research published as Exposure to air pollution and COVID-19 mortality in the United States: A nationwide cross-sectional study found a strong association: for every 1 microgram increase in the average population exposure to PM2.5 there was an 8% increase in Covid-19 mortality rate. 

Rachel explained the study used data on both Covid-19 related mortality and levels of particulate matter (PM2.5) in various urban and non-urban areas across the whole of the US. 

Given the argument rests on the association of data sets, various confounding factors were adjusted for, including population size, age distribution, population density, time since the beginning of the outbreak, number of individuals tested, weather, and socioeconomic and behavioural variables such as obesity and smoking.

Speculating on the causes of this strong association between poor air quality and Covid-19 mortality, Rachel explained that the damage caused by PM2.5 to both respiratory and cardio-vascular systems, is likely to increase the risk of death.

She also pointed out that until there is a vaccine it is important that environmental hazards – like poor air quality - that impact on the severity of the illness are considered and controlled.

Jonathan Grigg, Professor of Paediatric Respiratory and Environmental Medicine from Queen Mary University, set out the biological mechanism that might explain this association between pollution and Covid-19.

In his presentation he focussed on the infection rate of Covid-19 (rather than mortality rate) and showed that even short term exposure to particulate matter (this time the larger sized particles called PM10) can drive incidence of Covid-19 infection.

To infect cells, the virus needs a ‘way in’. Such an ‘entry point’ is provided by a substance called ACE2 that sticks to the cell wall and the study examined whether PM10 led to higher levels of ACE2.

ACE2 is found in the nasal and lung tissue and is a well-known factor for illnesses, for example smokers have higher levels and children have lower levels of ACE2 (which might be a factor in why the infection rate is lower in children).

The study used a Cyclone monitor on London’s Marylebone Road to collect particulates. Healthy lung cells were exposed to this substance and it was found that there was a ‘highly significant’ increase in ACE2.

Increases in ACE2 were identified across a range of PM10 levels – from 1 to 20 micrograms per cubic metre. The research has not been formally peer-reviewed but does point to a causal link between poor air quality and Covid-19 that explains the association shown in the US data. 

A recording of the meeting is available to view here