The: PM2.5/PM10 ratio expresses the anthropogenic share in atmospheric dusl. Very high values or this ratio, i.e. high contribution or PM2.5 to PM10. have occurred recently in atmospheric air within European indusuializcd areas. The paper compiles results of three year pair wise measuring ofconcentrations or PM2.5 and PM2.5-PM10 and compares shares or PMM2.5 in PM10 al three urban background sites in Upper Silesia Poland I towns or Zabrze. Katowice and Częstochowa). At all the three local ions, the PM2.5/PM10 ratio nr daily conccntrations nr dust only occasionally differed considerably from the PM2.5/PM10 ratios for the seasonal and yearly concentrations that, in turn. did not differ from the PM2.5/PM10 ratios al urban sites in Europe.

Polycyclic aromatic hydrocarbons (PAI-ls) are persistent organic pollutants, ubiquitous in the whole environment. They are relatively well known and are still of interest due to their well documented carcinogenic and mutagenie properties. In ambient air of urban regions they mostly occur as adsorbed to particles of suspended dust. The richest in these compounds and therefore most hazardous to humans, fraction of dust is the fraction of the finest particles. The paper presents results of investigations of dust sampled with use of an impactor Dekati PM10 in Zabrze, a site typical of Upper Silesian conditions. While sampling, the impactor segregates sampled particles into four fractions by their aerodynamic diameters. Sixteen PAHs were determined in each fraction chromatographically. PAH content in the fraction of the finest particles, i.e. in PM1, was of particular interest.

Froin January 2006 on, a continuous experiment consisting in determinations of granulometrie composition of the airborne dust has been performed in the Institute of Environmental Engineering of PAS, Zabrze. The investigations include measurements of concentrations of PM1 - the suspended in ambient air particles of the aerodynamic diameter not grater than I μm - by using the PM10 Dekali impactor. The results of twelve month measurements (January - December 2006) arc presented in the paper: the granulometrie composition of total suspended dust (PM10, PM2.5, PM1) in winter and summer at an urban background site in the Silcsian Agglomeration. Monthly and seasonal average concentrations of PM I O, PM2.5 and PM1 were computed.