Hudson River Dredging Project

What are PCBs?
The contaminant of concern at the Hudson River PCBs site is polychlorinated biphenyls (PCBs).
PCBs were widely used as a fire preventative and insulator in the manufacture of transformers and capacitors because of their ability to withstand exceptionally high temperatures. PCBs are considered probable human carcinogens and are linked to other adverse health effects such as
developmental effects, reduced birth weights and reducedability to fight infection.

PCBs are a group of chemicals consisting of 209 individual compounds, known as congeners. The congeners can have from one to ten chlorine atoms per molecule, each
with its own set of chemical properties. When grouped by the number of chlorine atoms per molecule, the term homologue is used. PCBs were sold in mixtures containing dozens of congeners. These commercial mixtures were known in the U.S. as Aroclors.

When released into the environment various processes can alter the pattern of PCBs from the original Aroclors. Analytical techniques vary and have improved over time. Congener-specific analyses were conducted for the Reassessment, but most of the older data was an interpretation of Aroclors. Therefore, a translation method was developed for the Reassessment to allow use of
historic and recent datasets on a common basis. The parameter common to all data sets is known as Tri+ PCBs, and represents the sum of PCBs with 3 to 10 chlorine atoms per molecule.

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