The society of the country influences contamination.

A... The pollution by organic one The occurrence sources of the organic one are various in the living drainage, the agriculture drainage, the factory drainage and so on. In the Europe and America, the sewage service for the processing of living drainage is moving ahead. However, in Japan, it is in 40 % of rates of diffusion and the low condition. At the developing nation, the living drainage which was and included urine is hardly processed except for the parts such as the city part and plainly, it is a state which is flowing in to the direct river and the lake marsh. B... an excess of nutrition It is the phenomenon which originates in the human activity on the lake and the river because the nutritional salt of the discharged organic one and nitrogen and phosphorus and so on flow in. The use as drinking water has become difficult because to do mold foul and to do alga foul have pricked water on the lake that is an excess of nutrition. Also, ecosystem itself of the lake, too, changes. It makes the environment that suited the growth of the creature that transmits contagious diseases and worms such as the malaria with the tropical and subtropical area. On the other hand, the excess of nutrition has the merit to improve the productivity of the fish, too.