1. Industrial Waste: Industries often release harmful chemicals, heavy metals, and other pollutants into waterways. This can be intentional dumping or accidental spills, and it can contaminate drinking water and harm aquatic life.

2. Agricultural Runoff: Fertilizers, pesticides, and animal waste from farms can wash into rivers, lakes, and oceans through rainwater. These pollutants can cause eutrophication (overgrowth of algae), which depletes oxygen and kills fish. They can also contaminate drinking water supplies.