Air pollution has been investigated from 1991 to 1994 in Trbovlje, Zagorje and Hrastnik, three towns in the Zasavje industrialized urban region in Slovenia. Cd and Pb were measured in aerosols continuously for three years employing direct electrothermal atomic absorption spectrometry, and polycyclic aromatic hydrocarbons (PAH's) for one year by gas chromatography and gas chromatography/mass spectrometry. In addition, SO2 and Black Smoke (BS) were monitored continuously during the period investigated. The study indicated that the concentrations of ail the pollutants measured were highest in the heating seasons. In the wintertime the average monthly concentrations of SO2 were up to 30 times higher than in the summertime, and the concentrations of BS up to 8 times higher. This increase being up to 6 times for Cd, and up to 10 times for Pb. PAH's, with the exception of naphthalene, were not detected in the summertime, while in the wintertime the presence of these carcinogenic substances was very evident. In general, the degree of pollution is comparable to other urban and industrialized regions worldwide. The results indicated the substantial decrease of air pollution during the period investigated. The main reason for declination of SO2, Black Smoke, Cd and PAH's pollution being in the progressive change of the local heating system from coal to gas and in the gradual substitution of coal in coal-fired heating station with oil. The reason for Pb pollution decrease being in a substantial reduction of the Pb content in leaded gasoline during the period investigated and in increased consumption of unleaded gasoline.
