Persistent Toxic Chemicals of Human Health Concern in Fish from San Francisco Bay and the Sacramento River, CA

ABSTRACT

As a result of a 1994 San Francisco Bay Regional Water Board study, the Office of Environmental Health Hazard Assessment issued an interim health advisory for people consuming fish from San Francisco Bay. This interim advisory remains in effect. In 1997 the Regional Monitoring Program for Trace Substances in the San Francisco Estuary (RMP) and the Sacramento River Watershed Program (SRWP) began monitoring fish contamination in the Bay and on the Sacramento River (River).

RMP sampling in 1997 targeted seven species that are frequently caught and eaten by Bay fishers and seven popular fishing areas in the Bay (Figure 1). Persistent toxic chemicals in Bay fish remained at concentrations of potential human health concern. Mercury exceeded a human health screening value in 44 of 84 Bay samples (Figure 2). All collected samples of leopard shark and striped bass exceeded the mercury screening value. White catfish from the Sacramento River also had relatively high mercury concentrations. Rainbow trout from the northern Sacramento River had the lowest mercury concentrations among the species sampled.

Concentrations of PCBs and other trace organics were highest in white croaker and shiner surfperch, the two species with the highest fat content in their muscle tissue. PCBs exceeded the screening value in 51 of 72 Bay samples (Figure 3). All of the white croaker and shiner surfperch samples exceeded the screening value for PCBs. Dieldrin, DDT (Figure 4), and chlordane had lower numbers of Bay samples above screening values: 27 of 72 for dieldrin, 16 of 72 for DDTs, and 11 of 72 for chlordanes. Rainbow trout from the northern Sacramento River watershed had relatively low concentrations of organic contaminants. White catfish from the Sacramento River had relatively low lipid content but moderately high wet weight concentrations.

Dioxins and dibenzofuran TEQs in all seven Bay samples analyzed exceeded the screening value of 0.15 ng/g wet weight. Dioxin-like PCBs accounted for 83% of the overall dioxin-like potency in these fish samples.

Significant variation in contaminant concentrations among Bay locations was observed. Oakland Harbor had significantly elevated wet weight concentrations of mercury, PCBs, DDTs, and chlordanes. Length-adjusted mercury concentrations were relatively high at Oakland Harbor and S.F. Waterfront. Lipid normalized concentrations of PCBs, DDTs, and chlordanes, and dieldrin were elevated at Oakland Harbor.

Mercury concentrations in the Bay in 1997 were not significantly different from concentrations in 1994. Statistically significant declines in concentrations from 1994 to 1997 were observed for PCBs, DDTs, chlordanes, and dieldrin. Dioxin ITEQs also showed a statistically significant decline from 1994 to 1997. Continued monitoring will be required to establish whether the declines observed are real indications of declining masses of contaminants in the Bay or due to variation in other factors.

Removal of skin from white croaker fillets reduced concentrations of PCBs, dieldrin, DDT, chlordane, and dioxins by 33 to 49%.

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Contents Abstract Introduction San Francisco Bay Conclusion: San Francisco Bay Sacramento River Delta Conclusion: Delta and River Figures 1. RMP fish sampling sites 2. Mercury concentrations in fish 3. PCB concentrations in fish 4. DDT concentrations in fish   5. Sacramento River Watershed fish sampling sites   6. Delta Fish Study Sampling sites Tables 1. Summary Statistics by species for mercury and organochlorines 2. Summary of concentrations in Bay Fish above screening values for each species

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