At the close of the 20th century, acid rain attracted considerable scientific and public attention due to its serious, widespread effects on ecosystems and its transnational nature, which prompted concerted governmental responses in North America and Europe. These initiatives, especially those taken under the UNECE Convention on Long-range Transboundary Air Pollution, significantly lowered air emissions and had a smaller negative impact on ecosystems. The policy agreements were built on a foundation of extensive scientific study, long-term monitoring, and integrated assessment modelling. We briefly outline the scientific results that served as the basis for the policy evolution in this paper, which is based on an international symposium held to mark 50 years of successful integration of air pollution research and policy. These initiatives, especially those taken under the UNECE Convention on Long-range Transboundary Air Pollution, significantly lowered air emissions and had a smaller negative impact on ecosystems.
