Sulphur dioxide, nitrogen oxides, fluorine and particulates are the main air pollutants in Cracow. In recent years the particulate emissions have dropped significantly without a parallel decrease in gaseous emissions. This entails a danger of acidifying the environment. To control gaseous pollutants is more difficult than to reduce particulates. It will thus be necessary to limit road traffic in the town centre (to control nitrogen oxides) and to eliminate small boiler houses (to control sulphur dioxide).