Where does water pollution come from?

While reduced emissions have helped Finnish lakes and rivers recover, they continue to be affected by diffuse pollution originating from extensive areas.

Around the middle of the 20th century, many water areas were affected by severe pollution caused by wastewaters from factories and settlements, or so-called point source pollution. Diffuse pollution from farming and forests was relatively minor.

This situation changed towards the end of the 20th century. Treatment of industrial and municipal wastewaters improved, reducing point source pollution to a fraction of its peak values. On the other hand, diffuse pollution was increased by such factors as more fertiliser being spread on fields, drainage of peatlands and a higher number of flushable toilets in rural areas and holiday homes.

Diffuse pollution has also started to decrease lately but has not yet been reduced enough. While a great deal of work has been put into water protection in agriculture, the results can only be seen with a delay, and farming remains by far the largest source of nutrient pollution in waters.

National emission statistics tell us nothing about local situations, however, and cities, factories, mines and peat extraction sites may continue to pollute their nearby waters. Harmful substances accumulated in the bottom sediment in earlier times may also be released back into the water, causing further problems.