Airborne particulates, especially fine particles and bound chemical compounds, are a potential mediator of adverse health effects. In this study an analysis was done of the concentration and size distribution of air particulate matter, the content of bound polycyclic aromatic hydrocarbons (PAHs), and the biological effects of organic extracts from different fractions of dust that had been influenced by urban and industrial emissions from the regions of La Plata, Argentina, and Leipzig, Germany, along with samples from control areas. Air particulate matter was sampled in summer and winter in each region using a high-volume sampler with a six-stage cascade impactor, classifying dust in six size fractions from 10-microm particles to those less than 0.49 microm in size. Organic extracts of dust were tested for mutagenicity (Ames test, Salmonella typhimurium TA98 strain, S9+) and cytotoxicity (Tetrahymena pyriformis test system, growth rate, cell respiration). The content of PAHs was analyzed by high-performance liquid chromatography (HPLC) with diode array and fluorescence detection. Mutagenic and cytotoxic effects were found to be associated with very fine (<0.49 microm) and fine (<1.5 microm) particle-bound compounds, corresponding to a higher content of PAHs. The mutagenic potency (revertants/m(3)) associated with particles less than 0.49 microm from urban areas of La Plata was about 1 order of magnitude higher than in particles in the range of 3.0 to 0.49 microm. Fine fractions from sites with an industrial burden were also found to exhibit high mutagenic potency. A similar tendency was observed in cytotoxicity tests with T. pyriformis. This cell system proved to be very sensitive to toxicants in tested dust fractions. The observed biological effects were found to be correlated significantly with concentrations of total PAH, carcinogenic PAHs, and benzo[a]pyrene.