Coronavirus: How Particulate Matter Accelerated Its Spread in Northern Italy
Can air pollution accelerate the spread of viruses like the coronavirus? Analyses by Italian researchers suggest it can. They found correlations between particulate matter (PM2.5, PM10) and the spread of COVID-19 in Northern Italy, and are therefore calling for restrictive measures to combat environmental pollution.
Airborne particulate matter is well suited as a transport carrier for many chemical and biological contaminants — especially viruses. Viruses, including the coronavirus, attach themselves to atmospheric particles (solid and/or liquid). These particles remain in the atmosphere for hours, days, or weeks, allowing a virus to spread over great distances too. The Italian researchers describe air pollution as a kind of highway for the coronavirus.
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Scientific studies on the spread of viruses in the population show that the incidence of viral infections correlates with concentrations of airborne particulate matter (e.g. PM10, PM2.5). For example, in 2016 a connection was observed between the spread of the syncytial virus (RSV) in children and particle concentrations. This virus causes pneumonia in children and is carried deep into the lungs by particles. The rate at which the infection spreads is linked to PM10 and PM2.5 concentrations.
Particulate matter acts as a carrier — and as a substrate
But particulate matter doesn't just act as a carrier — it also serves as a substrate that allows the virus to remain viable in the air for hours or days. How quickly viruses become inactive within these particles depends largely on the ambient conditions: while rising temperature and sunlight have a positive effect on the virus inactivation rate, high relative humidity can promote a higher spread rate of the virus, i.e. its virulence.
This general connection between air pollution from particulate matter and the spread of viruses like the coronavirus is now confirmed by findings from researchers at the Italian Society of Environmental Medicine (Sima), together with the universities of Bari and Bologna.
The researchers compared data from regional environmental protection agencies on exceedances of the legal particulate matter limit (50 micrograms per cubic meter average daily concentration, more on particulate matter limits in Germany) with reported coronavirus infection cases recorded by civil protection authorities.
Analysis of the coronavirus spread
The analysis revealed a relationship between exceedances of the legal limit values for PM10 concentrations, recorded between February 10 and 29, and the number of COVID-19 infection cases, updated to March 3 (taking into account a 14-day incubation period).
“The more particulate matter there is, the more highways are created for infection. It's necessary to reduce emissions to a minimum, in the hope of favorable meteorology." (Gianluigi de Gennaro, University of Bari)
According to the researchers, an “anomalous acceleration” was particularly evident in the Northern Italian Po Valley, coinciding two weeks later with the highest concentrations of atmospheric particles. The particles thus exerted a kind of boosting effect, a push toward the virulent spread of the epidemic.
"The high dust concentrations recorded in the Po Valley in February accelerated the spread of Covid-19. The effect is more clearly felt in the provinces where the first outbreaks occurred". (Leonardo Setti, University of Bologna)
For now, the scientists have published a position paper to present their hypothesis. The next step will be to consolidate the evidence in a broader study. “Until then, the concentration of particulate matter could certainly be regarded as a possible indicator or indirect marker for the virulence of the Covid-19 epidemic. Furthermore, according to the results of the ongoing study, the current safety distance during the Corona epidemic may not be sufficient everywhere, particularly at high concentrations of airborne particulate matter”, says Alessandro Miani, president of Sima.
In the researchers' view, it's important to actively improve air quality at home during times of quarantine and lockdown. Miani recommends opening windows several times a day for a few minutes, since mixing the air reduces the percentage of pollution. Air purifiers can also help significantly. It's also advisable to avoid activities that generate particulate matter (driving, smoking, grilling, etc). Because especially in narrow residential streets, existing particulate matter can act as a multiplier of infection and increase the risk of transmission.
The position paper is available for download here. And in this article we looked into whether air pollution increases the COVID-19 death rate.
Further sources:
(1) Ciencewicki J et al., 2007. “Air Pollution and Respiratory Viral Infection” Inhalation Toxicology, 19: 1135-1146
(2) Sedlmaier N., et al., 2009 “Generation of avian influenza virus (AIV) contaminated fecal fine particulate matter (PM2.5): Genome and infectivity detection and calculation of immission” Veterinary Microbiology 139, 156-164
(3) Ye Q., et al., 2016 “Haze is a risk factor contributing to the rapid spread of respiratory syncytial virus in children” Environ Science and Pollution Research, 23, 20178-20185