Heating and livestock farming suffocate the Po Valley.This is why the air is so polluted

Morphological factors have a significant impact, but do not fully explain the poor air quality of the Po Valley

Today the ranking according to which Milan is the third most polluted city in the world caused a sensation.A ranking drawn up by IQ Air, a private Swiss company producing air purifiers.The data is partial, as it refers to a specific moment, i.e. February 19th, does not take into account all global cities, but only a selection, and refers only to PM2.5.The alleged bronze medal of the city of Milan in the sad ranking infuriated the mayor Beppe Sala.But this does not take away the fact that for days the alarms about air quality in Italy and in particular in the Po Valley have been intensifying.

Hot, dirty air

The prolonged high pressure has brought atmospheric stability to the regions of Northern Italy and the absence of significant winds which, if present, could mix the air masses.The result is a continuous accumulation of pollutants in the air which during January and February was toxic for many days for anyone who breathed it, so much so that it made many ask whether it is worth going out to train or whether it makes sense to wear a mask all over the place. 'external (here are all the answers).This is a slowly improving situation which, in order to be resolved, must be addressed at its root by analyzing its causes.Of particular concern are PM10 and PM2.5.What do these acronyms mean?What are the main sources of these pollutants?One might think that industries and road transport have the greatest impact, but things are not exactly like that.

What are PM2.5 and PM10?

Airborne particles, referred to as PM10 and PM2.5, are microscopic fragments of dust, fumes, liquids, carbon derivatives and other materials suspended in the atmosphere.The name derives from their diameter:PM10s have a diameter of less than 10 microns, while PM2.5s are even smaller, with a diameter of less than 2.5 microns.One micron is equal to one thousandth of a millimetre.For comparison, a human hair is rarely thinner than 65 microns.These particles can be emitted by natural sources such as volcanic eruptions and forest fires, but are mainly produced by human activities such as domestic heating, vehicular traffic, industry, and intensive farming.

What are the health risks of airborne particulate matter?

PM10 and PM2.5 can penetrate deeply into human lungs, causing a variety of health problems.Smaller particles, such as PM2.5, can even reach the bloodstream and spread throughout the body, increasing the risk of cardiovascular disease, respiratory disease and other problems such as asthma, bronchitis, and cancers.Additionally, they can also worsen pre-existing conditions such as heart and lung disease.Therefore, reducing exposure to these particles is critical to protecting public health.

What are the sources of PM10?

Total PM10 emissions in 2021 decreased by 42% compared to 1990.An undeniable improvement but which still leaves the Po Valley in conditions of asphyxiation, with the 10 most polluted cities in the country all in this area according to the Legambiente report MalAria 2023.According to what the Higher Institute for Environmental Protection and Research calculates (Ispra), non-industrial combustion is responsible for 49% of the PM10 present in the air of Italian cities.The biggest impact in this sector is heating, specifically wood and pellet heating, which has led to an overall increase in particulate matter due to the air conditioning of buildings.Situation also illustrated by Alessandro Miani, president of the Italian Society of Environmental Medicine (Sima) a Open.

Miani explains:«In Lombardy, fireplaces and pellet stoves are also still widely used, which produce large amounts of dust.However, gas also produces pollutants.An electrification of heating systems is one of the solutions."Agriculture is responsible for 12% of PM10 in our country, while road transport is responsible for 10% of total particulate matter.A reduction has been recorded in this sector thanks to more stringent regulations on exhaust gases, but the share of particulate matter produced by the wear of brakes and tires continues to be significant.Industrial production then produces 15% of particulate matter.Minor sources are waste management, industrial machinery, the use of solvents and combustion for industrial purposes.

What are the sources of PM2.5?

The PM2.5 data does not differ much from that of PM10.Specifically, in this category road transport stands at 9% of emissions, while the already significant share of non-industrial heating and combustion rises, reaching 66%.Agriculture stops at 4% as does waste treatment and industrial processes, while those deriving from industrial machinery stand at 6%.

Which activities emit the most PM10 and PM2.5?

We often hear that intensive farming has a particular impact on fine dust emissions.Yet the item does not appear in the list of the most polluting sectors.This is due to a difference, that between primary and secondary particulate matter.According to an Ispra analysis prepared for the Corriere della Sera, in Italian cities there is more secondary particulate matter than primary particulate matter.Secondary particulate matter is formed in the interaction between fine particles already present in the atmosphere, other volatile and polluting compounds such as ammonia, nitrogen oxides and sulfur dioxide with climatic factors and solar radiation which determine an overall increase in fine dust.This explains the fact that livestock farms are among the major emitters of ammonia into the atmosphere.Combined, the percentages become the following.

Why does the Po Valley have such polluted air?

The Po Valley stands firmly as one of the most polluted macro-areas in Europe.This is due to a combination of several factors.Firstly geographical, since the Po Valley is closed on three sides by mountains that prevent air circulation, leaving a short outlet only on the small and also relatively closed Adriatic Sea.Furthermore, almost 15 million people live in the Po Valley, for a population density of 355 inhabitants per square kilometre, double the national one.The Northern regions are also those where the majority of productive activities and intensive farming are concentrated.

What is the role of traffic?

This is precisely the area of ​​the country where we note how data at a national level can show significant differences at a local level.Miani elaborates further:«Vehicle traffic accounts for 22% on a national basis, but in Milan it is more than double.Contrary to what one might think, the industrial department accounts for only 11% on a national basis as an emission source of air pollution, but in the North the concentration of industrial centers contribute more.Then there are agricultural activities, which in drought periods like today produce more dust."The same goes for intensive farming, which - Miani explains - produces "75% of all fine particles".

What are the solutions?

Beyond individual ones, there are various more or less immediate interventions that can be implemented to improve the situation.Miani identifies two main sectors:«urban greenery (green roofs, green walls, new plantings)».and «the nanotechnologies of photocatalic coatings on buildings».«These are transparent paints, also produced in Italy, with ethanol-based titanium dioxide.This typology is supported by scientific evidence and successfully tested.They are sprayed on surfaces and have two effects:they make them safe from vandalism and transform pollutants into by-products that are harmless to health, thanks to daylight.These paints are non-toxic to humans and make it possible to reduce pollution in a city by up to 30%", explains Miani.And again:«It is a solution that could be implemented immediately.The ideal would be to give tax incentives to private individuals to transform their condominiums into anti-smog systems and the public to invest in its buildings.These products, once applied, work for an average of 20 years and are not energy intensive."

On the cover:ANSA/TINO ROMANO | A view of the city of Turin with smog and pollution seen from the top of the Basilica of Superga on February 5, 2024