In 2011, the US EPA developed a Reference Concentration (RfC) for trichloroethylene of 2.0 µg/m3 based on two co-critical studies. One of the co-critical studies reported a dose-dependent increase in fetal cardiac malformations (FCM) in pregnant rats exposed to TCE via drinking water throughout pregnancy. As a result of concerns about this specific endpoint, some EPA regions and states recently issued interim action levels and response recommendations for TCE exposures from vapor intrusion based on accelerated timeframes meant to be protective of the developing fetus during the 3-week period in the first trimester during which the fetal heart develops. These actions have stimulated substantial debate about this particular endpoint within the scientific and regulatory communities, with some arguing that shortcomings of the in utero rat study should preclude it from being used as a co-critical study in the TCE inhalation risk assessment, while others argue that the overall weight of the evidence supports the conclusion that FCM is a sensitive adverse endpoint for TCE inhalation exposure, thereby justifying the use of the in utero rat study as a co-critical study. This session is intended to stimulate thought-provoking and open dialogue with members of the audience during a moderated panel discussion immediately following the scientific presentations. The moderated panel discussion will incorporate state-of-the-art tools in live audience polling to stimulate discussions. The goal of the roundtable is to identify the specific areas of agreement and/or disagreement and uncertainty regarding the toxicological evidence supporting the association between inhalation exposures to TCE and the potential for FCM and, through discussion, to develop strategies to help bring clarity to these areas.