Polychlorinated biphenyls (PCBs), which have been classified by EPA as a probable human carcinogen, are a class of chemicals present in the waters of the Delaware Estuary at concentrations up to 1,000 times higher than the water quality criteria. PCBs were used as coolants and lubricants in transformers, capacitors, and other electrical equipment because they don't burn easily and are good insulators. The U.S. banned the manufacture and general use (with a few exceptions) of PCBs in the late 1970s, but not before 1.5 billion pounds of the substance was produced.

Despite the ban, equipment containing PCBs is still in use due to the extended life span of the equipment. The chemical stability of PCBs led to their use in hundreds of industrial and commercial applications, but also allows them to persist in the environment to this day. PCBs enter fish and other wildlife through absorption or ingestion, and accumulate in their tissues at levels many times higher than in the surrounding water and at levels unsuitable for human consumption.

There are numerous sources of PCBs in the Delaware Estuary. They include contaminated sites, non-point sources, industrial and municipal point source discharges, the main stem Delaware River above Trenton, tributaries to the Delaware both above and below Trenton, the atmosphere, combined sewer overflows (CSOs), and the Atlantic Ocean.

Because high levels of PCBs have resulted in state-issued fish consumption advisories for certain species caught in the Delaware Estuary, these waters were and continue to be listed as impaired, requiring the establishment of a PCB total maximum daily load (TMDL). A TMDL expresses the maximum amount of a pollutant that a water body can receive and still attain water quality standards.

At the request of the three estuary states and the U.S. EPA, DRBC has taken the lead in developing the technical basis for PCB Total Maximum Daily Loads (TMDLs) for the Delaware Estuary (DRBC WQ Zones 2-6). The PCB TMDL for Zones 2-5 was established in 2003 and for Zone 6 in 2006. DRBC staff worked closely with the commission's Toxics Advisory Committee (TAC), an expert panel of scientists, and its TMDL Implementation Advisory Committee (IAC) on these efforts.

In 2013, DRBC adopted updated water quality criterion of 16 picograms/liter for polychlorinated biphenyls (PCBs) in the Delaware Estuary and Bay for the protection of human health from carcinogenic effects. This number, based upon the most current methodology and scientific data available, is now a uniform value for the entire Delaware Estuary and Bay (DRBC Water Quality Zones 2-6). The updated PCB criterion was developed under the guidance of the TAC. With DRBC's adoption of revised PCB criterion, it is anticipated that the U.S. EPA will establish new TMDLs (Stage 2 TMDLs) corresponding to the updated criterion.

To support TMDL implementation, DRBC monitors ambient waters, sediment, and fish tissue to provide precise and defensible data on PCB concentrations in the Delaware Estuary. Additionally, DRBC requires Pollutant Minimization Plans (PMPs) to track down and reduce point souce and non-point source PCB discharges.  

Important Links
DRBC Resolutions Relating to PCBs
Reports and Other Background Information