Researchers at Swiss Tropical and Public Health Institute conducted their study in 10 different cities, including Stockholm, Barcelona, Bilbao, Granada, Rome, Seville, Brussels, Vienna, Valencia and Ljubljana.
They found that around 14 percent of chronic childhood asthma could have been caused by near-road traffic pollution.
"This is the first time we have estimated the percentage of cases that might not have occurred if Europeans had not been exposed to road traffic pollution. In light of all the existing epidemiological studies showing that road-traffic contributes to the onset of the disease in children, we must consider these results to improve policy making and urban planning", lead researcher Dr Laura Perez said.
The study has been published in the European Respiratory Journal.