BACKGROUND: Estrogenic activity has been observed in several industrial and household products, and some evidence suggests that this activity may be linked to increased pathologies in humans and animals. Here, an engineered strain of Escherichia coli is evaluated for its ability to detect estrogenic activity in complex mixtures, including natural dietary supplements, hand and body washes, essential oils, and perfumes. The engineered E. coli biosensor strain expresses the ligand-binding domain of the human estrogen receptor beta (ER beta) as part of a larger allosteric reporter enzyme. The result is a simple bacterial growth assay, where estrogenic activity of a test compound is reflected by increased cell growth on a simple defined medium. RESULTS: While most consumer products did not yield a strong estrogenic response in the assay, a consistent estrogenic effect was observed with several perfumes. This effect is probably due to the presence of the known estrogen, benzophenone-2, which exhibited an EC50 concentration of 0.44 mu mol L-1 for the sensor strains used. CONCLUSIONS: This simple, bacterial biosensor is capable of rapidly and inexpensively detecting estrogenic activity in complex consumer products, and may eventually yield rough estimates of the equivalent estrogen doses associated with their use. (C) 2009 Society of Chemical industry