Measures taken by many industrialized countries in the 1970s to control urban and industrial air pollution (i.e. high chimney stacks) quite unintentionally sent increasing amounts of pollution across national boundaries in industrialized countries. During transport in the atmosphere, emissions of sulphur and nitrogen oxides and volatile hydrocarbons are transformed into sulphuric and nitric acids, ammonium salts and ozone. They fall to the ground, sometimes hundreds of thousands of kilometres from their origins, as dry particles or in rain, snow, frost, fog, and dew.
The Convention on Long-Range Transboundary Air Pollution was signed in Geneva in 1979 and entered into force in 1983. It has been ratified by 33 Governments and the EEC/EU. The convention is the first international legally binding instrument to deal with problems of air pollution on a broad multilateral basis. It constitutes the framework within which the Contracting Parties identify problems posed by transboundary air pollution and elaborate protocols on specific pollutants. Specific protocols to the Convention concern (a) the long-term financing of the European cooperative programme for monitoring and evaluation, (b) reduction of sulphur emissions, (c) control of emissions of nitrogen oxides and (d) control of emissions of volatile organic compounds.
The UK is the biggest source of lead pollution in the North Sea and of pollution causing acid rain in Norway. 93% of sulphur deposited in Austria (mostly as acid rain) has its origin outside the country, principally arising from the Czech and Slovak Federal Republic and former East Germany.