Published information on the input of pollutants to the North Sea has been used to identify the major pollutant pathways. Rivers and atmospheric deposition are the main input routes for metals, with the Rhine/Meuse and the Elbe contributing over half the riverine input. The dumping of estuarine dredging spoils results in a very large input of metals, which cannot be fully accounted for as a redistribution of riverine material unless the river inputs have been grossly underestimated. Rivers provide the largest input route for nutrients, but a substantial contribution is also made by direct discharges to coastal waters and estuaries. Sewage sludge dumping contributes less than 5% to the pollutant load to the North Sea.
Similar assessments have also been made for the Baltic Sea and the major UK estuaries.