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.