Diesel should not be cheaper than petrol as this only encourages people to opt for cars that run on a dirtier fuel, according to a consultant respiratory physician.

“Shifting to lower sulphur fuel and phasing out the Marsa power station were good moves. However, the price of diesel is still lower than petrol… There shouldn’t be any incentive to choose diesel over petrol,” Martin Balzan said. Petrol has been 9c per litre more expensive than diesel since April.

Dr Balzan’s comments came as  Volkswagen admitted that 11 million of its diesel vehicles were fitted with software that switched engines to a cleaner mode when they underwent official testing.

Dr Balzan was commenting following the release last week of data from a study called Respira, collected in 2012  at the European Respiratory Society Annual Congress in Amsterdam.

The study shows that elemental carbon, commonly referred to as soot, is much higher in Malta than in the US.

Respira saw a team from the Department of Respiratory Medicine studying the chemical composition of fine particles suspended in the air (pm2.5), and comparing the information with industrial Gela and rural southern Sicily. Malta has twice the level of particles found in Gela, and nearly three times more than rural Sicily. 

The chemical composition of such particles is very high in elemental carbon indicating diesel combustion as the main source.