Coronavirus: nitrogen dioxide emissions over Italy. Contains modified Copernicus Sentinel data (2020), processed by ESA, CC BY-SA 3.0 IGO

Coronavirus and pollution: many hypotheses, few certainties

The geographical distribution of the epidemic in the first few weeks and some studies taken from the media have raised the hypothesis of an association between atmospheric particulate pollution and the spread of Covid-19, a scientific issue on which many researchers are working in Italy and abroad.

The Italian Aerosol Society, which brings together 150 experts from universities, regional agencies and companies, recommends caution because there is the risk of mistaking coincidences for cause-effect relationships still to be proven.

Let's take stock of what is scientifically proven and what requires further research with Andrea Gambaro, Professor of Analytical Chemistry at Ca’ Foscari and member of the board of directors of the Italian Aerosol Society.

Is particulate matter bad for your health? Known

Gambaro and the other experts of the Italian Aerosol Society write: “It is known that exposure, more or less prolonged, to high concentrations of PM increases susceptibility to chronic respiratory and cardiovascular diseases and that this condition can worsen the health of infected persons. These high concentrations are frequently observed in northern Italy, especially in the Po Valley, during the winter period.”

Does Covid-19 spread where air is polluted? Unknown

“To date, there has been no evidence of greater susceptibility to infection by Covid-19 due to exposure to atmospheric dust. The claim that there is a direct relationship between the number of exceedances of PM thresholds and infections by Covid-19 is partial and premature. The effect of PM pollution on Covid-19 infection remains - in the current state of knowledge - a hypothesis that must be carefully evaluated with extensive and in-depth investigations.”

Does particulate matter carry the virus? Unknown

It has been hypothesized that atmospheric particulate matter can act as a carrier substrate for the virus, thus increasing the rate of infection. “This aspect is not confirmed by the knowledge currently available, in the same way as the life span of the virus on the surfaces and the factors that influence it are not yet fully known,” replies Gambaro.

Does the weather in the Po Valley favour the virus? Possible, but unknown

“It is possible that certain meteorological conditions, typically found in northern Italy in this period, such as low temperature and high atmospheric humidity, may create an environment that favours the survival of the virus,” the experts write. “These conditions, which generally coincide with a situation of intense atmospheric stability, favour the formation of secondary particulate matter and the increase in PM concentration close to the ground. The covariance between conditions of poor atmospheric circulation, formation of secondary aerosol, accumulation of PM close to the ground and spread of the virus must not, however, be mistaken for a cause-effect relationship. In the case of complex systems such as the system in question, the interpretation of simple correlations (i.e. between two time series) does not necessarily indicate a cause-effect relationship.”

Why reduce pollution? Known

“The proposal for restrictive measures to limit pollution as a means to fight infection is, in the current state of knowledge, unjustified, although there is no doubt that the reduction of anthropogenic emissions, if maintained for a long period, has beneficial effects on the quality of the air and climate and therefore on general health,” conclude the experts from the Italian Aerosol Society.