Current Knowledge and Data Needs for Dioxins in San Francisco Bay

San Francisco Bay was placed on the State of California’s 303(d) list of impaired waters in 1998 as a result of elevated concentrations of dioxins in fish. In 2008 the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) Dioxins Workgroup developed a workplan for reducing information gaps that were identified in a 2004 Conceptual Model/Impairment Assessment (CMIA) report on dioxins. Special studies in that workplan were largely completed by 2012, but continued monitoring of biota provided evidence of impairment and an opportunity for evaluating trends. Fish tissue concentrations indicate that the beneficial use of commercial and sport fishing is impaired by dioxins. Although there are dioxin-like PCBs also contributing to impairment, this report only directly addresses polychlorinated dibenzodioxins and furans (here collectively called “dioxins”).