Bisphenol A (BPA) is a man-made chemical present in a variety of products including food containers, receipt paper and dental sealants and is now widely detected in human urine and blood. Public health concerns have been fueled by findings that BPA exposure can influence brain development. In mice, prenatal exposure to BPA is associated with increased anxiety, aggression and cognitive impairments.  In response to public pressure, industry has begun to replace BPA with Bisphenol S (BPS). Cheryl S. Watson, from the University of Texas Medical Branch at Galveston (Texas, USA), and colleagues conducted cell-culture experiments to examine the effects of BPS on a form of signaling that involves estrogen receptors — the "receivers" of a biochemical message — acting in the cell's outer membrane instead of the cell nucleus. Where nuclear signaling involves interaction with DNA to produce proteins and requires hours to days, membrane signaling (also called "non-genomic" signaling) acts through much quicker mechanisms, generating a response in seconds or minutes.  Focusing on key biochemical pathways that are normally stimulated when estrogen activates membrane receptor, the researchers observed that BPS disrupts cellular responses to the hormone estrogen, changing patterns of cell growth and death and hormone release. Also like BPA, it does so at extremely low levels of exposure.  Reporting that: “Our studies show that BPS is active at femtomolar to picomolar concentrations just like endogenous hormones —that's in the range of parts per trillion to quadrillion," the lead investigator warns that: “Those are levels likely to be produced by BPS leaching from containers into their contents."