The release of reactive oxygen intermediates (ROI) from bovine alveolar macrophages (BAM) after stimulation with heavy metal-containing dusts was investigated. BAM were obtained by postmortem lavages of bovine lungs. The dusts were collected from waste incineration, sewage sludge incineration, an electric power station, and from two different factories. Three quartz dusts were used as heavy metal-free controls. The dusts were fractionated by sieving and sedimentation and analyzed by electron microscopy, atomic absorption spectrometry (AAS), and atomic emission spectrometry with inductively coupled plasma (AES-ICP). Incubation of BAM with the dusts (12.5-1000 micrograms/ml medium) led to concentration-dependent increases in ROI release. The secretion of ROI was already seen after 15 min and lasted throughout the experiment up to 90 min, with the exception of a waste incinerator ash, which contained the highest contents of some heavy metals and where the release of ROI ceased after 60 min. We suggest that this dust exhibits simultaneously stimulating and inhibiting effects. The ratio of the secreted O2- and H2O2 varied, depending on the dust being investigated. The release of hydrogen peroxide correlated best, in descending order, with the content of iron, manganese, chromium, vanadium, and arsenic in the dusts.