The study, which involved 360,000 residents across 13 EU countries, found that the health dangers from pollution might be even greater than previously thought.
Out of the cities surveyed, Turin residents were found to have the greatest exposure to fine particles of pollution, known as PM2.5, which contribute to heart and lung disease and can lead to lung cancer.
Two surveys conducted for the report for Turin, Italy's car manufacturing capital, recorded 30.1 and 30.0 microgrammes per cubic metre of the particles – above the EU's recommended 25 microgrammes per cubic metre and four times more than those recorded in Stockholm, which is the cleanest city.
When combined with the death rates of participants during the study, Turin’s results were alarming, the report found.
“Prolonged exposure to tiny particles of soot or dust found in traffic fumes and industrial emissions may be more deadly below current EU air quality limits than previously thought,” the study said.
Scientists said that for every five-point increase, the risk of dying from natural causes rose by seven percent. Prolonged exposure to pollution was significant even when the results considered other factors such as whether the residents smoked or were overweight.
Claudia Galassi and Ennio Cadum, from the Turin-based Piedmont Environment Agency (ARPA), told The Local the city's poor air quality was combination of factors.
“The high level of traffic, the high concentration of industrial plants, the emissions from domestic heading and above all the particular climate of the area,” all contributed to high levels of pollution, they said via email.
Turin sits in the Po Valley and as a result pollution becomes trapped, a phenomenon which does not often happen in other European cities, Galassi and Cadum said.
Pollution levels in Turin were also found to be far higher than in Rome, which registered 19.4 microgrammes per cubic metre. Overall, countries in southern Europe performed worse than their northern neighbours.
A 2012 European Environment Agency (EEA) study said that along with ozone, fine particles were the “most problematic” pollutants to human health.