The word bioaccumulation is used to describe the build up of chemicals in fish. Through the food chain, chemicals like PCBs, DDT, dioxins, and mercury build up in the bodies of the fish. The picture below shows how this might happen in a lake near you People are at the top of this food chain. When you eat a lot of fish that have chemicals in them, those chemicals can build up in your body, too. While the chemicals in fish won’t make you sick right away, they could cause health problems someday. If you eat a lot of fish that have these types of chemicals in them, the chemicals can build up and stay in your body, too. This could someday cause health problems, like cancer or diabetes, in some people. Not everyone will get sick, though. Some people may be fine after years of eating fish with these chemicals in them. Others may have health problems. Bioaccumulation of chemicals is the problem concerning all living organisms. This is the result of dynamic equilibrium between the uptake and elimination. The extent to which bioaccumulation occurs determines the toxic effects which are manifested. In some cases, the mechanisms of protection from certain undesirable substances deposited in special sites, to prevent their participation in the metabolic reactions, have evolved.