they are either washed down into the soil or into the water bodies. from the soil, these are absorbed by the plants along with water and minerals. from the water bodies they are taken up by aquatic plants and animals. this is one of the ways in which they enter the food chain. as these chemicals are not biodegradable, they get accumulated progressively. as human beings occupy the top level in any food chain, the maximum concentration of these chemicals get accumulated in our bodies. this phenomenon is known as biological magnification.