It showed that urban concentrations of nanoparticles, which measure just a few millionths of a millimetre, could reach several hundred thousand in a cubic centimetre of air.

Then a pendulum, consisting of a tube of metal about one cubic centimetre [long] and a short string was swung above the battleship.

In the 'cleanest' car, an upmarket saloon, the researchers recorded an average of 75 particles in each cubic centimetre and a maximum of 2,400.

The cleanest car, an upmarket saloon, had an average of 75 particles per cubic centimetre and a maximum of 2,400.

Standing on the deck, downwind of a ship's funnel, investigators found air pollution of 84,000 ultrafine particles per cubic centimetre.