This chapter addresses sources and trends of atmospheric pollutants and deposition in relation to the Baltic Sea region. Air pollution is shown to have important effects, including significant contributions to nitrogen loading of the Baltic Sea area, ecosystem impacts due to acidifying and eutrophying pollutants and ozone, and human health impacts. Compounds such as sulphate and ozone also have climate impacts. Emission changes have been very significant over the past 100 years, although very

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... fferent for land-and sea-based sources. Land-based emissions generally peaked around 1980-1990 and have since reduced due to emissions control measures. Emissions from shipping have been steadily increasing for decades, but recent measures have reduced sulphur and particulate emissions. Future developments depend strongly on policy developments. Changes in concentration and deposition of the acidifying components generally follow emission changes within the European area. Mean ozone levels roughly doubled during the twentieth century across the northern hemisphere, but peak levels have reduced in many regions in the past 20 years. The main changes in air pollution in the Baltic Sea region are due to changes in emissions rather than to climate change.