Air pollution is one of the most important risk factors of respiratory diseases. We found worsened health indices in 10 year–old children (n = 61; age = 10.4±0.4 years; height = 142±7 cm; mean ± SD) during a 1986 study in one of the most pollution endangered regions of Bulgaria (total suspended particulate matter, TSPM = 520±61 mg/m 3 ; mean ± SE and annual mean concentration of SO2 = 98±19 mg/m 3 ; mean ± SE). Both vital capacity (VC) and forced expiratory volume in 1 s (FEV1) were consistently lower (X = 88.5 % and 82.5 %, respectively) than Bulgarian reference values. Because of the strong industrial decrease in this region in recent years, the air pollution was reduced significantly: in 1989 TSPM was 460±40 mg/m 3 and SO2 = 60±10 mg/m 3 ; in 1992 – 350±27 mg/m 3 and 60±9 mg/m 3 , and in 1996 – 187± 9 mg/m 3 and 60±12 mg/m 3. In 1996 we conducted a study in the same region to determine the effects of reduced outdoor air pollution on children's lung function. A comprehensive lung function assessment was performed on 97 children (mean age 10.4±0.6 years, height = 145±6 cm). The FEV1 and VC were 103±9% and 100±9% respectively. There was a tendency of lower values of MEF50% (94±9%) and Single Breath Transfer Factor – TL,CO (93±9%). Children with passive smoking home exposure had lower values of TL,CO than those of the remainder by 4.4% (p = 0.038). In conclusion, the results of this study convincingly indicate that the reduction of main industrial pollutants is followed by improvement of lung function indices.

        Key words: air pollution, pulmonary function, children