Food Chain/Web

Food webs all over the world have become contaminated by insecticides and other manufactured chemicals. Some of these compounds are having profound effects on the reproduction and behavior of some wild animal species. These chemicals were released into the environment because it was believed that their concentrations were too small to have an effect on organisms. Now we know better. Contamination of very remote habitats, such as the Antarctic and the Arctic, has convincingly demonstrated that even small amounts of certain compounds can have massive effects. Some of these compounds are persistent hydrophobic (water-fearing) contaminants accumulating in the fatty tissues of organisms because they do not dissolve in water.

Some of the most important persistent, hydrophobic contaminants are PCBs and DDT. PCBs, or polychlorinated biphenyls, are a suite of about 209 different compounds, each with slight variations in their chemical structure. PCBs were widely used as insulating material in electric transformers and for other purposes. There is currently a worldwide ban on their production and use but large quantities still persist in the environment. DDT, or dichlorodiphenyltrichloroethane, is an insecticide that has been dispersed all over the world. Unfortunately, both PCBs and DDT now occur in all plant and animal tissues even in remote areas where they were never used (for example, in animals such as polar bears and seals). Humans are also contaminated, and mothers pass these chemicals to their babies in their milk, which is rich in fat where DDT and PCBs concentrate.