to screen other types of chemicals and endocrine effects. Based on recommendations from an advisory panel, the agency expanded the screening program to include male hormones, the thyroid system, and effects on fish and other wildlife. The basic concept behind the program is that prioritization will be based on existing information about chemical uses, production volume, structure-activity and toxicity. Screening is done by use of in vitro test systems (by examining, for instance, if an agent interacts with the estrogen receptor or the androgen receptor) and via the use of in animal models, such as development of tadpoles and uterine growth in prepubertal rodents. Full scale testing will examine effects not only in mammals (rats) but also in a number of other species (frogs, fish, birds and invertebrates). Since the theory involves the effects of these substances on a functioning system, animal testing is essential for scientific validity, but has been opposed by animal rights groups. Similarly, proof that these effects occur in humans would require human testing, and such testing also has opposition. After failing to meet several deadlines to begin testing, the EPA finally announced that they were ready to begin the process of testing dozens of chemical entities that are suspected endocrine disruptors early in 2007, eleven years after the program was announced. When the final structure of the tests was announced there was objection to their design. Critics have charged that the entire process has been compromised by chemical company interference. In 2005, the EPA appointed a panel of experts to conduct an open peer-review of the program and its orientation. Their results found that "the long-term goals and science questions in the EDC program are appropriate", however this study was conducted over a year before the EPA announced the final structure of the screening program. The EPA is still finding it difficult to execute a credible and efficient endocrine testing program. As of 2016, the EPA had estrogen screening results for 1,800 chemicals. Europe In 2013, a number of pesticides containing endocrine disrupting chemicals were in draft EU criteria to be banned. On 2 May, US TTIP negotiators insisted the EU drop the criteria. They stated that a risk-based approach should be taken on regulation. Later the same day Catherine Day wrote to Karl Falkenberg asking for the criteria to be removed. The European Commission had been to set criteria by December 2013 identifying endocrine