Even brand new cars can be dangerous. Australian scientists warned in 2001 that while many motorists may like the smell of a new car, that odour is actually indicative of high levels of toxins, which can make people ill. They can persist inside the car six months or more after leaving the showroom.

The toxins include benzene, which can cause cancer; acetone, which can irritate the nose, throat and lungs; ethylbenzene, which can affect the nervous system; and xylene isomers, which can affect a baby's development in the womb.

'People who buy new cars should make sure there is plenty of outside air entering the vehicle while they drive, for at least six months,' said the head of the research study, Dr Steve Brown.