Calor has found a striking way of describing the pollution in Queen Street, Oxford, by suggesting a day of inhalations there would fill you with as much nitrogen dioxide as 61 cigarettes.

The alarmist imagery will not be to everyone's taste but the firm's survey makes a telling and timely point: our city's air owes more to the traffic squeezed into it than to the rural acres which surround it.

The accuracy of Calor's remarkable league table is difficult to assess. The claim that Oxford is the worst city in the country for pollution surely cannot be true.

But the survey serves as a warning that we need to do much more to clean up our city.

A quicker replacement policy for old, smelly buses, and a rule that requires bus drivers to switch off their engines at stops will be a good start.