Inhalable particulate dusts are involved in the genesis of several lung diseases. Besides the well-known toxic dusts, i.e. asbestos and quartz, heavy metal-containing pollutants are considered as possible harmful substances. In the present study we compared the effect of silica chemically coated with certain metal oxides on several cell physiological parameters of bovine alveolar macrophages (BAM). The cytosolic free calcium concentration [(Ca2+)i], the intracellular pH (pHi), and the plasma membrane potential (MP) of BAM were measured by flow cytometry whereas the dust- induced secretion of reactive oxygen species (ROS) was measured enzymatically. Compared to control incubations with pure silica the dust-induced secretion of ROS by BAM was not affected when the particles were coated with Cr2O3, NiO, and Fe3O4, whereas VO2-coated dust induced a marked increase in ROS release. This effect was not correlated to changes in (Ca2+)i, pHi, or MP. On the other hand Cr2O3-coated silica caused alterations in all of the three latter parameters. The same pattern of changes has been reported previously for quartz dusts (Tarnok et al., Anal. Cell Pathol., 15:61-72, 1997). We conclude that cell physiological measurements by flow cytometry could extend the pallet of tools to evaluate possible toxic effects of environmental dust samples.