Toxicity testing with bioassays using luminescent bacteria has grown steadily in recent years. In the present assay we used a bioluminescent bacterium Escherichia coli – lux (E. coli-lux) as an indicator organism for detecting toxicity from household dust in indoor environments. After incubating E. coli-lux cells with diluted dust extractions, the BL reading was taken as a measure of the proportion of living bacterial cells in the reaction mixture and EC50 values were red from the dose-response curve where 50 % of bacterial cells were killed. E. coli-lux test from settled dust samples correlated with microbial growth and symptoms in target buildings. According to our results, E. coli-lux toxicity assessment can be used to generate information about toxic properties of dust samples which could help to evaluate the risks of contaminated indoor environments.