In the field of endocrine disruption, so-called ‘low dose’ effects, non-monotonic dose responses (NMDRs), the existence or otherwise of thresholds for toxicity, mixture effects at low doses, and critical windows of exposure are challenging the current paradigm of toxicity testing and risk assessment of chemicals (Zoeller et al, 2012; Vandenberg et al, 2012, UNEP/WHO, 2013). As a result the European regulation on plant production products (1107/2009), the revisions to the biocides Directive (COM267) and the regulation concerning chemicals (Regulation (EC) No. 1907/2006 ”REACH”) only support the marketing and use of chemical products on the basis that they do not induce endocrine disruption in humans or wildlife species. Nevertheless the EFSA Scientific Opinion on the Hazard Assessment of Endocrine Disruptors (EFSA, 2013), and the earlier EFSA Scientific Colloquium on Low Dose Response in Toxicology and Risk Assessment (EFSA, 2012), both suggest that there is no reason why endocrine disrupters (EDs) should not be subject to risk assessment and regulated accordingly. The issues on “low dose” effects listed above imply a possible need to make modifications either to the risk assessment paradigm or to current test methods, or both. Furthermore, neither the EFSA Colloquium nor the more recent Workshop on Low Dose Effects and Non-Monotonic Dose Responses for Endocrine Active Chemicals (Beausoleil et al, 2013) were able to reach consensus about the importance, or even the existence, of these phenomena (see Zoeller et al, 2012; Vandenberg et al, 2012; UNEP/WHO, 2013). This difficulty in reaching consensus is partly due to uncertainty caused by the quality of some of the data used to support these concepts, and partly due to a lack of understanding about putative underlying mechanisms of toxicity.