If you live where there is planted field nearby then you have chemicals in the air, water, and soil. Organic fields use chemicals deemed safe for the product but not for the environment. No farmer wants to waste water and food for weeds but why care about weeds in a yard? Mow or weed them short and they look just fine. Round Up works by increasing the growth of the plant so much it can't keep up with itself and dies out. Really like a turbo Miracle Gro.