The UN/ ECE Convention on Long-range Transboundary Air Pollution (CLRTAP) has over the years substantially contributed to the development of international environmental law and has created the essential framework for controlling and reducing the damage to human health and the environment caused by transboundary air pollution. In the years from its entering into force (1983) until today problems of acidification and eutrophication due to anthropogenic emissions of sulphur and nitrogen compounds as well as damage to individual receptors like human health, surface waters, vegetation, materials and cultural heritage by air pollutants were in the main focus of the effects oriented work under the Convention.