Due to the complex composition of organic dust it is difficult to point at one or a few components causing pulmonary health problems in different occupational environments. The aim of the present study was to develop a method which aims at measuring the general potential of organic dust to inflict a pulmonary inflammation regardless of the actual composition of the dust. The bioassay is based on measurement of interleukin-8 (IL-8) secretion from a lung epithelial cell line (A549) 24 hours after addition of test compound. The test compounds for method development and characterization were different types of lipopolysaccharide (LPS) and glucans, formaldehyde, methyl methacrylate (MMA), 2,4-dinitro chlorobenzene (DNCB), nickel sulphate, and sodium dodecyl sulphate (SDS). The dust samples were liquid extracts from cotton dust, compost dust, school dust samples, and dust from household waste. The bioassay had a linear dose-response relationship when stimulated with LPS from Escherichia coli up to 180 mg/ml. The day-to-day variation was reduced when the estimated potency factor was corrected relatively to the IL-8 secretion obtained with the positive controls. Three types of LPS induced IL-8 secretion in the bioassay. The potency of LPS from Klebsiella pneumoniae was 2-3 fold higher than the potency of LPS from E. coli and Pseudomonas aeruginosa. Two glucans from yeast did not induce IL-8 secretion, whereas Curdlan (glucan from a Gram-negative bacterium) did, but part of the activity was due to a soluble compound perhaps indicating an active non-glucan contamination of the sample. Formaldehyde had a potency similar to that of LPS from K. pneumoniae, whereas nickel sulphate had a much weaker potency. In contrast, the contact allergens DNCB and MMA did not induce IL-8 secretion, neither did the irritative ionic detergent SDS. The experiments on liquid extracts of different organic dust samples revealed profound differences. The potency of extracts of the two cotton dust samples was similar to the potency of the extract of compost dust. However, the extract of compost dust was far more cytotoxic. In comparison, the potency of liquid extracts of samples from a school was up to 10 fold higher than the potency of the cotton dust and compost samples. A preliminary experiment on dust from household waste suggested that the insoluble part of dust may have a potency 10³ to 10⁴ fold higher than the potency of liquid extracts of dust.