There are different grades of pollution. The first are substances that stimulate illness. These substances are bacteria, viruses and monocellular which live in sewage and trash. The second grade in pollution is oxygen consumption pollution. This is digested by oxygen using bacteria. When these bacteria convert the pollution, the oxygen disappears from the water. All the organism in this waters, will die because the oxygen shortage. The third grade enclose the inorganic pollution that will solube in the water. Examples of this are acids, salt, and metals. When there is a large number of this pollution in the water, it can’t be used as drinking water and the vegetation in the water will die. Even nutrient will pollute the water. Some substances such as nitrates and phosphates will stimulate the grow of algae and water vegetation, and using all the oxygen. This causes fishes to die. Organic substances can pollute the water, examples are oil, plastic and pesticide. These are harmful for humans, animals and vegetation in the water. The most dangerous grade of pollution is sediment. The sediment will prevent the water to absorb the light. Radioactive substances which are dissolvable in the water, could cause cancer, birth handicaps and genetic harm.
