Authorities need to get heavily polluting trucks off the roads of Athens if they are going to clean up the city’s air, according to a study by the National Technical University of Athens which found they are responsible for 60 percent of the capital’s pollution.

Many of the trucks that are withdrawn from circulation in Western Europe reappear on Greek roads, burdening the atmosphere with their high-pollution emissions, transport experts say. “The result of this practice is that the average age of trucks in this country is 17 or 18 years when in most Western European countries it is around 11 years,” said Yiannis Ziomas of the university’s chemical engineering department.

These trucks run on diesel, which releases a higher proportion of pollution particles into the atmosphere than other types of fuel. The bad maintenance of these vehicles contributes to the toxic emissions they release.

The fact that such trucks are often used for deliveries to stores in the city center also intensifies the smog.