The ocean -- it is a vast sea of blue that is the home of millions of aquatic animals. It is the source of our waters, our rains; the animals that live within it are a source of food in almost every county. Even though it is so important however, humans still do not treat it with much respect. Up until 1977, there was a toxin known as polychlorinated biphenyls (PCBs), which are synthetic, consisting of around 207 different chemicals. It had popular use as a lubricant in electrical equipment because it did not burn easily. However, through the production of these PCBs, they entered into the atmosphere though the air, soil, accidental spills, disposal, and use in electrical equipment. Many of these PCBs made their way into the ocean, causing many adverse affects.
PCBs are very slow to decompose, and so, they last for a very long time. The water spreads out the PCBs in the ocean, but when sea life comes along these particles attach themselves to the sea creatures, and slowly collect. In Environmental Issues in Oceanography, Second edition the authors [Daniel C. Abel and Robert L. McConnell] state that, "While seawater concentration is usually below 1 part per million (ppm) concentrations exceeding 800 ppm have been measured in the tissues of marine mammals, which would qualify as hazardous waste!" This is quite a disturbing occurrence when you think about how many fish humans consume, or how much water we consume.
The affects of PCBs vary; exposure to them can range from having no effect to causing major cancers, such as liver cancer. Most commonly seen are skin rashes and irritation. According to the Environmental Health Perspective "For over a decade, in utero and postnatal exposure to PCBs has been linked with reduced IQ in children, but exactly how the chemicals exert their effects on cognitive functioning remains uncertain.".
Tributyltin (TBT) is another chemical commonly found in the water.