Endocrine disruptors (EDs) are hormone-like substances that can have undesirable effects on health. For example, chemicals can increase the risk of breast cancer if they act in a manner similar to the female sex hormone estrogen. Animal experiments are still required to detect the hormonal effects of chemical substances. A test has now been developed at the German Center for the Protection of Laboratory Animals (Bf3R) that tests the effects of hormones on cultured human cells.