The effect of alkaline dust pollution emitted from Bartin cement plant on the soil microbial biomass carbon was investigated using the chloroform fumigation-extraction (CFE) method. Microbial biomass C (C(mic)) values ranged from 157.82 to 1201.51 mu g g(-1) soils in the polluted area and from 726.70 to 1529.14 mu g g(-1) soils in the control area. Soils polluted with alkaline cement dust resulted in significant reductions in C(mic) levels compared to control soils. Microbial biomass C correlated negatively with CaCO(3) content (r = -0.52, P < 0.05) and positively with soil organic C (r = 0.67, P < 0.01). C(mic):C(org) ratio proved to be a reliable soil microbial parameter for describing the change in the man-made ecosystem. Mean C(mic):C(org) ratio was 2.55 and 3.09 in the polluted soils and control soils, respectively. The decrease in this ratio was an indication of soil degradation in the polluted soils. A significant decline in the C(mic):C(org) ratio in cement dust-polluted soils also indicated that this parameter can serve as a good indicator of soil health.