The United States and the European Union (EU) have engaged in a long-standing and acrimonious trade dispute over the EU's decision to ban hormone-treated meat. Despite an ongoing series of dispute settlement proceedings and decisions by the World Trade Organization (WTO), there is continued disagreement between the United States and the EU on a range of legal and procedural issues, as well as the scientific evidence and consensus concerning the safety of hormone-treated beef. To date, the EU continues to ban imports of hormone-treated meat and restricts most meat exports to the European Union to a limited quantity of beef imports that are certified as produced without the use of hormones. Starting in 1981, the EU adopted restrictions on livestock production limiting the use of natural hormones to therapeutic purposes, banning the use of synthetic hormones, and prohibiting imports of animals and meat from animals that have been administered the hormones. In 1989, the EU fully implemented its ban on imports of meat and meat products from animals treated with growth promotants. Initially the ban covered six growth promotants that are approved for use and administered in the United States. The EU amended its ban in 2003, permanently banning one hormone-estradiol-17-while provisionally banning the use of the five other hormones. As part of this dispute, the United States suspended trade concessions with the EU by imposing higher import tariffs on EU products. The first U.S. action in 1989 imposed retaliatory tariffs of 100% ad valorem duty on selected food products, and remained in effect until 1996. The second U.S. action in 1999 again imposed a 100% ad valorem duty on selected foods from EU countries. Over the years, the United States and the EU have attempted to resolve this dispute through a series of WTO dispute consultations, settlement panels, arbitration proceedings, and formal appeals. One of the earlier WTO panel decisions in 1997 ruled against the EU on the grounds that the ban is inconsistent with the EU's WTO obligations because the EU had not conducted a risk assessment. In response, the EU commissioned studies and reviews to address the scientific basis of its ban on hormone-treated meat. The EU reaffirmed its position that there are possible health risks associated with hormone-treated meat, given the available scientific data. The EU claims it has complied with its WTO obligations and has challenged the United States for maintaining its prohibitive import tariffs on EU products. The United States disputes whether the EU has conducted an adequate risk assessment to support its position and maintains there is a clear worldwide scientific consensus supporting the safety to consumers of eating hormone-treated meat. In October 2008, the WTO issued a mixed ruling allowing the United States to continue its trade sanctions, but allowing the EU to maintain its ban. In January 2009, the U.S. Trade Representative (USTR) announced its intent to make changes to the list of EU products subject to increased tariffs under the dispute, including changes to the EU countries and products affected, and higher tariffs on some products. The EU claimed this action constituted an "escalation" of the dispute. In May 2009, following a series of negotiations, the United States and the EU signed a memorandum of understanding (MOU). As part of this MOU, the EU granted new market access to U.S. exports of beef raised without the use of growth promotants, and the United States suspended its retaliatory tariffs on certain EU products. However, in December 2016, USTR took steps to reinstate retaliatory tariffs on the list of EU products under the dispute given continued concerns about U.S. beef access to the EU market. This issue has also been raised in ongoing trade negotiations between the United States and the EU to establish a free trade area as part of the Transatlantic Trade and Investment Partnership (T-TIP).