35. Discarded refuse
The contaminating component of foods that are discarded in tourists areas and resorts is broken down by rain, seeps into the ground and flows into rivers, thereby polluting the rivers and lakes.
36. Traffic congestion
The fourth cause of contamination is atmos-pheric pollution. The sulfur and nitrogen oxides discharged by vast numbers of automobiles rise into the atmosphere and fall as acid rain, snow and fog, pollute the land and plant life and eventually flow into the rivers.
37. A mountain forest
Acid rain falls over the entire land surface of the islands of Japan and, as in northern Europe, the U.S. and Canada, causes the pH to increase to a value of 4.5. This value tends to weaken the process of photosynthesis in plants and has a strong impact on all forms of aquatic life from microorganisms to fish.
Since the amount of rainfall in Japan is almost three times that of northern Europe, though, there has been no great damage yet. Even so, it does threaten to deteriorate the quality of the water.
38. Spreading agricultural chemicals
The fifth cause of contamination is pollution due to agricultural chemicals and chemical fertilizers. In contrast to the concentration of population in the cities, the rural population, which shoulders the responsibility for the production of food, continues to decline year after year and the number of farm workers has now dropped to a mere 4.8% of the total population.
