Because PCBs found in the environment are composed of a variety of chlorinated compounds, there can be broad ranges in their availability to organisms. In general, the more chlorinated are less available in the environment because the higher chlorinated congeners are less soluble and less volatile. These higher chlorinated pollutants tend to concentrate in the sediments and the particulate material suspended or found in the bottom of rivers, lakes and coastal waters.
Concentrations in the sediments can be thousands of times higher than in the overlying waters. Organisms such as clams, snails, microorganisms, and others accumulate the contaminants associated with the bottom sediments far above concentrations found in the overlying waters. Fish and other freshwater or marine organisms accumulate pollutants in their tissues and when eaten by higher organisms, pass the pollutant to higher life forms, including humans.
