When these cleaners are rinsed down the drain, they contaminate our water source.  Some of the chemicals that are washed down the drain are removed at wastewater treatment plants, but some remain, making their way back into rivers and lakes. When in the water, these toxic chemicals cause massive overgrowth of certain plants, crowding out wildlife. When the plants die in large masses, they deplete oxygen in the water, killing off more plants and marine life.