Tallinn is the capital of Estonia, located by the sea (the Gulf of Finland, a part of the Baltic Sea) in the north-western part of the country at latitude 59°25', longitude 24°45'. In 1996 the resident population in Tallinn was approximately 430 000 persons, which since 1990 has decreased by about 10%.

In the 1990's there has been great changes in emission structure, when emissions from traffic have increased while emissions from stationary sources have decreased due to closing down of many industrial plants. Point source emissions have decreased by 40% for NO₂ and by 70% for SO₂ between 1990-1995 because of the decreasing production in heavy industry. In the centre of Tallinn there are no big point sources. The large heating plants in the Tallinn area use natural gas and heavy oil as fuel, and they are located 2 km (Ülemiste) and 4 km (Mustamäe) from the centre.

The main air pollution source of nitrogen oxides and VOC in Tallinn at present is traffic. According to Tallinn Vehicle Registration Centre there were 154 604 personal cars, 1860 buses and 21 196 heavy vehicles registered in Tallinn in January 1998, which makes approximately 400 vehicles per 1000 inhabitants. Due to an increasing number of new cars, the usage of unleaded gasoline is increasing. The market rate for leaded gasoline is approximately 5-7%.