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Initiated due to the public outcry against the detrimental impacts of Acid Rain in Europe, the Convention on Long-range Transboundary Air Pollution (CLRTAP) was signed in 1979 and entered into force in 1983. As the first regional environmental convention, CLRTAP has been instrumental in the reduction of key harmful pollutants in both Europe and North America.

With 51 parties out of UNECE’s 56 member States, the Convention covers most of the region. Over the past 30 years, the Convention has been extended by 8 Protocols, focused upon setting strict reduction targets for releases of pollution for the protection of human and environmental health. Each of these Protocols targets pollutants such as sulphur, nitrogen oxide, persistent organic pollutants, volatile organic compounds, ammonia, and toxic heavy metals.

Over the years, the Convention has contributed to drastically reducing in the level of pollutants in the region:

    * Between 1990 and 2006, SO2 levels have dropped by 70% within the European Union, and by 36% in the United States
    * Between 1990 and 2006, NOx levels have dropped by 35% within the European Union, and by 23% in the United States
    * Between 1990 and 2006, Ammonia (NH3) levels have dropped by 20% in the European Union
    * Between 1990 and 2006, non-methane volatile organic compounds have decreased by 41% in the European Union
    * Between 1990 and 2006, primary particulate matter (PM 10 ) has declined by 28% in the European Union

As the Convention moves forward, it has incorporated the new findings and concerns into an integrated approach with multiple targets aimed at addressing multiple effects. The 1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-level Ozone went into force in 2003, and focuses upon reducing harmful impacts via establishing stricter targets for SO2, NOx, VOCs and ammonia.

The Protocol will soon be revised to include more pollutants. The ongoing renegotiations of the Heavy Metals Protocol and Persistent Organic Pollutants Protocol will also present both stricter targets and emphasize new pollutants (including dissolved solvents, dust and particulate matter).

European Union

The European Community’s member countries were some of the first to sign and ratify the Convention. Over the past 30 years, some of the greatest declines in harmful air pollutants have been witnessed here. The European Commission’s Directorate–General for the Environment (DG Environment) has a specific strategy for cooperation with CLRTAP, focusing on 3 key areas: the development and use of air pollutant models, establishing reliable emissions inventories and defining a common approach on air pollution effects.

The work conducted by the European Union, for compliance with CLRTAP, was recently presented in a report issued by the European Environmental Agency, summarizing air pollution emissions data in each country from 1990 to 2007. The EU’s commitment to conducting relevant research provides a significant contribution to the understanding of the current state of air pollution and its detrimental impacts.

North America

The transboundary effects of air pollution triggered both Canada and the United States to ratify the Convention during its earlier years. Both nations recognized that lowering emissions in North America as well as Europe would be crucial for the reduction of air pollution and its impacts. Canada and the United States implement the provisions of the Convention through bilateral agreements: cooperating on long-range transport of air pollutants under the 1991 Canada–U.S.

Air Quality Agreement, the Great Lakes Binational Toxics Strategy, and (with Mexico) under the Commission for Environmental Cooperation and the Border Air Quality Strategy. Among the achievements this cooperation has produced are the Acid Rain and Ozone Annexes to the Canada–U.S. Air Quality Agreement, with a commitment to reduce emissions of sulphur dioxide, NOx and VOCs.

Eastern Europe, Caucasus and Central Asia

CLRTAP is increasingly focusing upon providing expertise and guidance to Eastern European, Caucasus and Central Asian nations in their initiatives to comply with the Protocols and reduce impacts from air pollution. This year, the Persistent Organic Pollutants (POPs) Protocol, Heavy Metals Protocol and Gothenburg Protocol will be renegotiated to include stringent targets coupled with provisions for flexibility to provide these nations the opportunity to replace their older technology and better monitor pollutants.

In addition, the Convention continues to assist these nations with guidance in developing policies and efficiently implementing the Protocols; actions which will prove to be effective in reducing emissions and protecting their populations’ health and environment. This year alone, CLTRTAP’s Secretariat has undertaken projects to assist the Russian Federation, Kazakhstan, Belarus, Moldova, Albania, Bosnia Herzegovina, Montenegro, Serbia and the Former Yugoslav Republic of Macedonia.

Emerging issues

Although much has been accomplished in the past 30 years, scientific research continues to identify new risks and emissions targets. In response, CLRTAP is increasing its focus on the addition of new pollutants including dissolved solvents, dust, and fine particulate matter (PM 2.5) amongst others. Climate change is a major environmental challenge, and both greenhouse gases and air pollutants have largely the same source and their effects can be closely linked.

It is a challenge for the future of CLRTAP to make progress in maximizing the benefits to be gained from policies to address both climate change and damage from air pollution. Thus, the Convention recognizes the importance of working in an integrated manner with respect to climate change, and has started a dialogue with other international agreements such as the United Nations Environment Programme (UNEP)’s Stockholm Convention (addressing persistent organic pollutants) and the future mercury convention, to further explore these links and possible solutions.


United Nations Economic Commission for Europe (UNECE)
Environment, Housing and Land Management Division
Palais des Nations
(+41-22) 917-2356 or
(+41-22) 917-2346)
Telefax: (+41-22) 917-0107/917-0621
Email: air.env@unece.org