Bath is a World Heritage City and many of its most important buildings are made of Bath Stone. The structure of Bath Stone is particularly vulnerable to attack by the acids resulting from sulphur in the atmosphere.
Since the sulphur content of the air was reduced by implementation of the Clean Air Act, scientific tests show that the rate of attack is increasing, not decreasing as was intended. This has been shown to be the result of increased nitrogen oxides (NOX) from traffic fumes, which act as a catalyst and speed-up the rate of acid attack.

False Colour Picture of Chemical Action on Bath Stone   Click here for more details

The facades of some buildings are already irreversibly damaged to a depth of 1 cm below the surface and will crumble in the near future.

The geography of Bath, in a 'bowl' surrounded by hills, traps airborne pollution and allows the concentration of traffic fumes to rise to levels which are dangerous to health. This bowl shape also makes a Ring-Road almost impossible to construct , so there is no way of diverting the through-traffic from the city centre except through other local routes.

Replacing petrol-engined vehicles with diesel-engined ones will change the mix of pollution but will not remove it. Diesel engine exhaust is a major source of spongy carbon particles (PM10s) which adsorb quantities of dangerous chemicals on their surface. PM10s are so small that they evade the body's defences and are deposited in the lungs where the chemicals are deposited to the detriment of health.
Diesel exhaust particles also blacken buildings and the unburnt fuel particles form a film which promotes algal growth.

More about Pollution in a Heritage City?

More about Bath's Traffic Problems?