Polychlorinated biphenyls in the Great Lakes

This chapter reviews the scientific understanding of the concentrations, trends, and cycling of polychlorinated biphenyls (PCBs) in the Great Lakes. PCBs were widely used in the Great Lakes region primarily as additives to oils and industrial fluids, such as dielectric fluids in transformers. PCBs are persistent, bioaccumulative, and toxic to animals and humans. The compounds were first reported in the Great Lakes natural environment in the late 1960s. At that time, PCB production and use was near the maximum level in North America. Since then, inputs of PCBs to the Great Lakes have peaked and declined: sediment profiles and analyses of archived fish indicate that PCB concentrations have decreased markedly in the decades following the phase-out in the 1970s. Unfortunately, concentrations in some fish species remain too high for unrestricted safe consumption. PCB concentrations remain high in fish because of their persistence, tendency to bioaccumulate, and the continuing input of the compounds from uncontrolled sources. PCBs are highly bioaccumulative and many studies have shown that the complex food webs of the Great Lakes contribute to the focusing of PCBs in fish and fish-eating animals. PCB concentrations in the open waters are in the range of 100-300 pg L, and are near equilibrium with the regional atmosphere. PCBs are hydrophobic yet are found in the dissolved phase of the water column and in the gas phase in the atmosphere, and they continue to enter the Great Lakes environment. The atmosphere, especially near urban-industrial areas, is the major source to the open waters of the lakes. Other sources include contaminated tributaries and in-lake recycling of contaminated sediments. Until these remaining sources are controlled or contained, unsafe levels of PCBs will be found in the Great Lakes environment for decades to come. © Springer-Verlag Berlin Heidelberg 2006.