In Lombardy, one of the most polluted regions among OECD — Organisation for Economic Co-operation and Development — member countries, the lockdown imposed to limit the spread of Covid-19 brought all movement to a halt, causing a sharp drop in fine particulate matter and nitrogen dioxide (NO₂) pollution emissions. Fine particulate matter, PM2.5, fell by 22 per cent, while nitrogen dioxide concentrations dropped by 36 per cent. These findings come from a study carried out by researchers at the Rff-Cmcc European institute on economics and the environment (Eiee), which calculated that the reduction in pollution saved approximately 22,500 years of life.

The effects of lockdown on pollution

Using artificial intelligence tools such as machine learning, the researchers were able to explain and calculate the number of years of life (in terms of premature deaths) saved thanks to the reduction in air pollution, through a lowering of the risk of cardiovascular and respiratory diseases among Lombardy's inhabitants. Medical literature does indeed attribute to air pollution from fine particulate matter (PM2.5) and nitrogen dioxide (NO₂) the capacity to cause harm to human health.

"From February to May, the reduction in PM2.5 saved around 8,500 years of life in Lombardy. The reduction in NO₂ saved around 22,500," explained Francesco Granella, an Eiee researcher and lead author of the study.

Emissions of the two pollutants go hand in hand, making it difficult to clearly distinguish the health effects of one from those of the other; for this reason, the two values were not added together to obtain a total number of years of life saved.

By comparing the hours of life saved with the number of deaths caused by Covid-19 in the same region and over the same period (nearly 16,000, accounting for around 192,000 years of life lost in the region), the study concludes that more than 10 per cent of the years of life lost to Covid-19 were saved by the reduction in air pollution brought about by the lockdown measures" — an exceptional situation that provided a unique natural experiment for assessing the relationships between local air pollution and different emission sources.

The threat of air pollution to health

The study provides important information for policymakers in shaping future anti-pollution measures.

"These analyses remind us of the severity of the effects of air pollution, which in Italy is responsible every year for twice as many deaths as those attributable to Covid-19 to date. This data is extremely useful for understanding how a profound green transformation of the economy can deliver health benefits for citizens," said Massimo Tavoni, director of Rff-Cmcc, European institute on economics and the environment (Eiee) and professor at the Politecnico di Milano.

Emissions from the transport sector fell sharply, those from industry fell partially, while emissions from building heating and agriculture were unaffected, or only marginally so, by the lockdown. This explains the greater reduction in NO₂, attributable mainly to the decline in road traffic, compared with the reduction in PM2.5, which is more closely linked to other sectors that were not equally impacted. Policies aimed at reducing pollution must necessarily cover these sectors too, and be tailored to seasonal patterns, the study suggests.