Since 1975 we have collected 45 samples of airborne particulates at various locations of the highly industrialized Rhine–Ruhr district (Germany), using a high volume sampler equipped with glass fibre filters. Samples were extracted by organic solvents and quantitatively transferred to dimethyl sulphoxide for tissue culture experiments. Nearly all of the 45 samples of airborne particulates induced cytotoxic effects on mammalian cells in vitro in a dose-dependent manner affecting cell functions and structures. Impairment of phagocytosis at lower concentrations and loss of cell viability at higher concentrations of extracts of airborne particulates was demonstrated in cultures of rodent and human macrophages. Furthermore, a dose-related reduction of plating efficiency of diverse mammalian cell lines (Syrian hamster kidney line 14-lb, Chinese hamster lung cell line in 79 and/or human pulmonary alveolar type II cell line A 549) in the presence of extracts was detected. As a sensitive bioassay for mutagenicity testing, induction of sister chromatid exchanges in human lymphocyte cultures revealed that low quantities of extracts exerted a strong genotoxic activity. Furthermore, a remarkable enhancement of malignant cell transformation was observed in the presence of the majority of extracts at very low concentrations utilizing cultures of Syrian hamster kidney cells infected with Simian virus (SV-) 40. We must consider a permanent body burden and a health risk in humans from inhalation of airborne particulates from polluted areas as indicated by cytotoxic, mutagenic and carcinogenic activity on mammalian cells in vitro.