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PCBs in the Bay
This page of the EcoAtlas Demonstration provides links to maps and data for
PCB concentrations compiled from four
different studies in the San Francisco Bay Area. Polychlorinated biphenyls (PCBs) are synthetic organic chemicals that were
manufactured in the U.S. for a variety of industrial applications from 1929 to
1979. Their environmental persistence, adverse effects, and accumulation in
the food web led to a ban on the manufacture and sale of PCBs in 1979. PCBs
are currently a contaminant of concern in the San Francisco Estuary because
of the health threat to humans and wildlife. Two common guidelines used to
evaluate sediment quality are the "Effect Range Low" (ERL) guideline, which
is considered the threshold for possible adverse effects to aquatic life,
and the "Effects Range Median" (ERM) guideline, which is considered the
threshold for probable adverse effects. The PCB ERL is 23 ppb, and the ERM
is 180 ppb. These guidelines were developed by the National Oceanic and
Atmospheric Administration." To assess the extent of PCB contamination
of the San Francisco Estuary, recent monitoring efforts have measured PCB
concentrations in sediment throughout the Estuary and its watersheds. For comparison of PCB concentrations in sediment collected from different
locations in the Bay Area, data were evaluated from studies that used similar
methods of collection, analysis, and quality assurance. These studies include
the San Francisco Estuary Regional Monitoring Program for Trace Substances
(RMP), the Bay Protection Toxic Cleanup Program
(BPTCP), which included a Pilot Regional Monitoring
Program, a study of contamination in San Leandro
Bay, and a study of PCB and mercury
contamination in stormwater conveyance systems in the watersheds of the San
Francisco Estuary. |