Why is fertilizer considered a pollutant if it is needed by plants?

Dear Student

Fertilizers are considered as pollutants because

1. They dissolve in water and pollute it.
2. If the excess water from the field flows to a lake or river, then overgrowth of algae will happen and the other organisms in water will not be able to survive.
3. Overuse leads to infertility of the soil. The soil may become too acidic or too basic.

Regards