농도가 가장 높은 곳은 영국 북서부 머지강과 어웰강, 4위는 캐나다 세인트로런스강, 5위는 독일 라인강 지류의 마인강이었다.
The areas with the highest concentrations were the northwestern Mersey and Awell rivers; fourth was the St. Lawrence River in Canada and fifth was the Main River of the Rhine, Germany.