Inside Italy: Why is air pollution in northern Italy so bad?

Local Italy

08-02-2025

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Earlier this week, Italian environmental watchdog Legambiente released its latest report on air pollution in major cities across the country.
The report found that 25 of 98 Italian cities monitored had exceeded the legal threshold for coarse particulate matter, or PM10, in 2024 (the limit is set at a maximum of 35 days a year with a daily average of over 50 micrograms of PM10 per cubic metre).
According to Legambiente, average PM10 levels exceeded the 50-microgram limit on a total of 70 days in Frosinone, giving the Lazio city the title of Italy's 'smog capital' for the second consecutive year.
Besides Frosinone however, only three other non-northern cities (Naples, Catania and Terni) were found to have violated clean air ordinances in 2024.
The remaining 21 urban centres, including Milan, Turin, Verona and Venice, were all located in the Po Valley, in the north of the country.
High levels of air pollution in the region, which straddles Piedmont, Lombardy, Veneto and Emilia-Romagna, covering an area of around 48,000 square kilometres, shouldn't come as a surprise.
In recent years, the Po Valley has consistently been ranked by experts among the areas with the worst air pollution in the entire European continent.
A 2023 study by academics at Utrecht University and Switzerland's Tropical and Public Health Institute found that more than a third of people living in the region breathed air whose concentrations of PM2.5 particles were four times the World Health Organisation's guideline limit.
A 2023 investigation conducted by the European Data Journalism Network also found that Lombardy's Milan, Cremona and Monza were the three worst European provinces for air pollution, as average annual PM2.5 levels exceeded 21 micrograms per cubic metre in all cases.
Why does all of this matter?
PM2.5 (fine particulate matter) and PM10 (coarse particulate matter) are both regarded by scientists as dangerous to human health.
These particles are small enough to be inhaled into the lungs, where they can cause a range of health problems, particularly for people with existing respiratory conditions such as asthma.
Long-term exposure to high levels of particulate matter has also been linked to cardiovascular and respiratory diseases, as well as an increased risk of lung cancer.
What makes the Po Valley so heavily polluted?
A number of different factors contribute to the Po Valley being one of the worst places for air pollution in Europe, according to experts.
Firstly, the Pianura Padana is among the most heavily industrialised areas on the continent: Lombardy is the top industrial region in the EU, with Veneto (6th) and Emilia Romagna (9th) also figuring in the top ten.
This translates to high levels of emissions - mainly nitrogen oxides - derived from industrial combustion and manufacturing or refinery processes.
But with over 23 million residents (around 40 percent of the national population), the Po Valley is also a very densely populated area.
This results in very high local concentrations of pollutants (especially particulate matter and nitrogen oxides) derived from domestic heating and road traffic.
The region's weather conditions and the influence of nearby mountain ranges are also believed to contribute to pollution.
According to meteorologist Flavio Galbiati, the Alps and Apennines surrounding the Po Valley 'affect the wind regime, whose intensity is generally very weak'. This contributes to relatively lengthy periods of air stagnation.
Secondly, the area frequently experiences a phenomenon known as 'thermal inversion' during the cold months: the 'layer' of air close to the ground becomes colder (and heavier) than the layer above it, which prevents it from rising through the atmosphere.
This creates a 'clog that prevents air circulation, trapping pollutants close to the ground, where their concentration can only increase day after day.'
What's being done about this?
While the area's geographical features cannot be changed, the transport, agriculture and heating sectors could all be regulated to reduce pollution and protect public health, according to Legambiente.
This would include a gradual switch to fully electric public transport, the phase-out of combustion vehicles and heating devices using non-renewable sources, and environmentally-friendly urban planning.
But regional authorities in the Po Valley have so far failed to take meaningful and decisive steps, voicing concerns that many of the required measures would damage the local economy.
Even more alarmingly, they have often openly opposed new EU policies aimed at reducing pollution.
In May 2023, the regional heads of Veneto, Lombardy, Piedmont and Emilia Romagna all opposed EU directives setting out stringent emission limits and environmental targets to be met by 2030.
Lombardy's president Attilio Fontana called the new rules 'unreasonable'.