Synthetic dyes are dangerous in different ways. They pollute the drinking water and the fields we grow our food on. Factories dump their chemical waste into rivers causing a lot of this pollution: These factories are usually next to large waterways (rivers or lakes) because making and using synthetic dyes takes a lot of water. Therefore, the factories become a threat to these waters – and to the people and animals that live near them because the poisoned water is unsuitable for drinking, growing food, or raising fish for example.