Poland was the sixteenth State to ratify the Convention, 12 June 1997 the Convention entered into force ninety days later on 10 September 1997 ( latest status ). The Convention was opened for ratification, acceptance, approval and accession from 3 September 1991.

This was followed by the Convention’s signature by the European Community (now European Union) and twenty-nine States in the period up to 2 September 1991. The Senior Advisers, at their fourth session held in Espoo (Finland) from 25 February to 1 March 1991, adopted the Convention on 25 February 1991 (session report ECE/ENVWA/18). Six negotiating meetings followed, from October 1988 to September 1990. The Senior Advisers subsequently agreed to establish an ad hoc meeting to elaborate a draft. The Group of Experts recommended to the Senior Advisers the development of a framework agreement on EIA in a transboundary context. In the absence of papers from member States, Mr Connelly drafted a summary focussing on EIA in a transboundary context. The rapporteur for the topic 'EIA in Specific Circumstances' was Robert Connelly (Canada). Then later in 1987 the ECE Group of Experts held a seminar on EIA in Warsaw.

In January 1987, the UNEP Group of Experts on Environmental Law elaborated the concept of EIA in a transboundary context.

By the early 1980s, EIA procedures were in place in a number of ECE member States and, in 1982, a Groups of Experts on EIA was established under the Senior Advisers to ECE Governments on Environmental and Water Problems. In 1975, the Final Act of the Conference on Security and Cooperation in Europe referred to ECE to follow up on the concept of environmental impact assessment (EIA). The Conference on the Human Environment, held in Stockholm in 1972, asserted the responsibility of States to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States or of areas beyond the limits of national jurisdiction (principle 21 in the Declaration ).

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