Pollutants may be loosely defined as any material that degrades the environment. Fertilizers promote growth of algae and aquatic vegetation beyond what is naturally sustainable. This growth reduces water clarity, often covering the entire surface of a pond or lake. Excess nitrate levels from fertilizer can contaminate drinking water supplies. This is particularly a problem in ground water.
Many pesticides are harmful to aquatic organisms, and some are dangerous to humans as well.
Insecticides are a particular concern because of their effects on aquatic insects, which many other organisms rely upon as a food source. Pesticides also may be leached into soil and even ground water, posing expensive cleanup costs and health concerns. Cleaning Supplies and Disinfectants. Many everyday products such as cleaning supplies and disinfectants can also be damaging to the environment. A slug of such material can wreak havoc if spilled in a small stream.