RMP News Volume 1, Issue 2

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Regional Monitoring News, Fall 1995

Contents

PCBs in the San Francisco Estuary
RMP Monitoring Basics
Fish Contamination
Teaching About Watersheds Conference
Staff Contacts
Evaluating the Ecological Health of the Estuary
Staff Profile: Bruce E. Thompson
Calendar
Announcements

The ABCs of PCBs in the San Francisco Estuary

by Jay Davis

Polychlorinated biphenyls (PCBs) are a class of contaminants that are currently of great concern in the Estuary. RMP results from 1994 show that PCB concentrations in waters of the Estuary are uniformly greater than an EPA water quality criterion. In addition, a study conducted by the San Francisco Bay Regional Water Quality Control Board in 1994 found that PCB concentrations in fish collected throughout the Bay exceeded screening values for protection of human health, resulting in the issuance of an advisory for consumption of Bay fish. 

These recent findings are surprising in light of the fact that PCBs have been unavailable commercially and subject to restricted uses for almost two decades. How can PCBs still be a problem in the Estuary? The answer to this question lies in a combination of the extreme persistence of these compounds, their biomagnification in the food web, continuing sources, and careless disposal in the past that has led to widespread contamination on both a local and global scale. 

Sources of PCBs

Due to their resistance to electrical, thermal, and chemical processes, PCBs were used in a wide variety of applications from the time of their initial commercial production in 1929. The primary uses of PCBs were as insulating materials in electrical capacitors and transformers, hydraulic fluids, plasticizers in rubber and synthetic resins, carbonless copy paper, and lubricants. Smaller quantities were used as pesticide extenders and in inks, waxes, and other applications. In 1966 came the first report that PCBs were widespread environmental contaminants. By the 1970s a growing appreciation of the severity and ubiquity of environmental PCB contamination led to restrictions on PCB production and use. Commercial production of PCBs in the U.S. ceased in 1977. 

The Estuary has served as a receptacle for a significant quantity of PCB residues. A detailed inventory of the sources of PCBs to the San Francisco Estuary has not been compiled. In general,...