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FISH
Chemical Contamination in San Francisco Bay
1995
Study Results, June 1995
A report has been released on the concentrations of contaminants in certain fish species throughout the bay. This fact sheet produced by the San Francisco Bay Regional Water Quality Control Board and Office of Environmental Health Hazard Assessment (OEHHA) summarizes information on this study.
Why was this study conducted?
The San Francisco Bay Regional Water Quality Control Board has conducted a study to measure the levels of chemical contaminants in fish caught by anglers in San Francisco Bay. A committee of state agency representatives, anglers, and environmental groups designed the pilot study. The study design was expanded to provide enough information for the Office of Environmental Health Hazard Assessment (OEHHA) to analyze the information collected to develop advice on consumption of fish in the bay to protect public health.
Which fish were tested and where did the fish come from?
Fish were collected for the study between May 2 and June 10, 1994, by the Department of Fish and Game. The fillets of fish were then analyzed for potentially harmful chemicals. Fish collected are representative of fish that are commonly caught and eaten, and are more likely to be contaminated because of their fat content and feeding habits. White croaker was the highest priority fish collected. Shiner surfperch, walleye surfperch, leopard sharks, brown smoothhound sharks, striped bass, sturgeon and halibut were also collected. The map shows the 13 different locations where the fish were collected for the study.
How were the 13 locations chosen?
The locations were chosen to represent all areas of the bay, frequently fished shorelines or piers, potentially contaminated areas, and locations where levels of contamination are considered low.
What chemicals were found in the fish collected?
The fish collected were tested for over 100 chemicals. Of these chemicals, six were found at levels of concern. These chemicals were PCBs, mercury, DDT, dieldrin, chlordane and dioxins. OEHHA has developed information sheets describing these chemicals and the potential health effects from contact with them. You may obtain this information by calling the Pesticide and Environmental Toxicology Section of OEHHA at (510) 622-3170 in Oakland or (916) 327-7319 in Sacramento.
How do chemicals in the San Francisco Bay fish compare with other locations?
Two similar studies on chemicals in fish have been conducted by OEHHA in the Santa Monica and Monterey bays. In general, the level of PCBs and DDT in sportfish from San Francisco Bay were similar to or lower than the levels in Santa Monica Bay for the same fish species, but higher than those in Monterey Bay. The highest levels of PCBs in sportfish from the San Francisco Bay are about five to ten times lower than found in the Great Lakes area, where they occur extensively. Chlordane levels in fish from San Francisco Bay were similar to levels found in other areas of the state. Dioxins were not measured in many of the samples from the Santa Monica or Monterey Bay studies. Dioxin levels in San Francisco Bay were not higher than the average background levels found in other areas of the country, but are still of concern because of the extreme toxicity of this contaminant. Mercury has been found at higher levels in several inland lakes in California, and is the most common contaminant of concern nationally.
Are chemical levels in San Francisco Bay going down?
The California Mussel Watch program has been measuring levels of contaminants in mussels throughout the state for over 15 years. Mercury levels in mussels have remained at essentially the same level during this time. Long term trends for DDTs, chlordanes and PCBs indicate that levels of these chemicals have steadily been going down since the beginning of the program. We expect these trends to continue because DDT was banned in 1972, chlordanes were phased out beginning in 1975, and PCBs were banned in 1979. Dieldrin and dioxins have not been measured through the California Mussel Watch program.
Are some sites "safer" to fish from than others?
Since this study was designed as a pilot study and not a comprehensive study, samples could only be collected at a limited number of locations. In addition, since different species were caught at different stations, a comparison of stations is difficult. However, some generalizations can be made: Vallejo-Mare Island was the sampling location from which fish most often contained high levels of contaminants. Oakland Inner Harbor also had fish that tested high in levels of contamination. OEHHA is evaluating the data reported from the limited samples in the study to find out whether some sites are safer for fishing than others. More studies may be required. OEHHA is also conducting a detailed assessment of the health concerns related to the chemical levels in the study. Until more information is available, OEHHA has provided guidelines about how much Bay fish you can safely eat, as described in this fact sheet.
What are the health concerns from eating sport fish in the bay?
The principal health effects of concern are potential nervous system changes in developing fetuses, infants, and small children (e.g., impaired mental and motor development), mainly associated with excessive mercury or PCB exposure, and potential increased risks of cancer due to exposure to PCBs, dioxins, and the pesticides. There is some indication of greater sensitivity of the nervous system of fetuses, infants, and young children. Because of this sensitivity more restrictive consumption advice is given for young children and pregnant or breast-feeding women who may pass the chemicals on to their fetus or child.
What advice do you have for people eating sport fish in San Francisco Bay?
OEHHA has issued an interim consumption advisory covering most fish species from the bay, as follows:
Adults should limit their consumption of San Francisco Bay sport fish to, at most, two meals per month. (A fish meal is considered to be an 8 oz. portion prior to cooking of fish for a 154-pound [70 kilogram] person. If you choose to eat sportfish from the San Francisco Bay, the amount of fish eaten should be adjusted according to body weight, with roughly 1 ounce of fish per 20 pounds body weight. For a 40-pound child, for example, a fish meal would be 2 ounces of fish.)
Adults should not eat any striped bass over 35 inches.
Women who are pregnant or may become pregnant, or who are breast-feeding, and children under 6, should not eat more than one meal of Bay fish per month and, in addition, should not eat any meals of shark over 24 inches or striped bass over 27 inches.
This advisory does not apply to salmon, anchovies, herring, and smelt caught in the bay; other ocean-caught sport fish; or commercial fish.
This advisory supersedes the existing advisory on striped bass in the bay, but does not revoke the recent advisory issued for the Richmond Harbor Channel Areas.
Are all fish in the bay contaminated?
All of the fish species sampled in this study contained levels of contaminants that pose a concern and are thus included in the advisory. Other fish species that were not sampled but are included in the advisory because they are expected to have similar levels of contamination are rockfishes, flatfishes, sculpin, and rays.
Although salmon, anchovies, herring, and smelt were not tested in the pilot study, they are expected to have lower contamination levels because they spend most of their lives in the sea or because their diets differ from the targeted species.
Large striped bass and large shark cause a particular concern because as predator fish they can accumulate higher levels of methylmercury. Fish with high fat content tend to have higher levels of contaminants because some chemicals, such as PCBs, are stored in the fat. White croaker had the highest level of PCB contamination in the fish species tested.
Will I get sick if I eat more than the recommended amount of fish?
At the levels found in the bay fish, the chemicals should not make you sick from eating just occasional meals or from eating a large amount of fish at one time. Fish are a good source of protein in the diet, and OEHHA does not suggest that you completely stop eating the fish that you catch in the bay.
Some of the health hazards, such as infant development problems, are documented in laboratory tests and have been seen in people who had a much greater exposure to the chemicals in food than the levels found in bay fish. Other potential effects are not as well studied. The risks of cancer, for example, are not certain and may actually be zero. Cancer would potentially develop only after years of eating large amounts of the fish regularly.
Limiting fish meals as recommended in the interim advisory should protect you from any of the adverse health effects. More specific recommendations will be issued when a thorough evaluation of the study data is completed by OEHHA in conjunction with other public agencies.
How can you make the fish safer to eat?
There are several ways to make fish safer to eat. These are explained in an illustrated pamphlet available from OEHHA. (1) Fish should be cleaned and gutted, and the guts should not be eaten because they tend to accumulate more chemicals; (2) skin and trim fat from the fish because chemicals are stored in fat, including the fat under the skin; and (3) bake, broil, steam, or grill fish on a rack so that the juices from the fat drip off during cooking. Throw out the juices. Deep frying in vegetable oil or poaching will also remove some of the fat, but discard the liquid after cooking.
Is there other general advice on safe fishing practices?
Yes. OEHHA also offers some general advice to make fishing safer. This includes (1) fish at a variety of places, or a place known to have low contaminant levels, rather than one usual spot that might have high levels; (2) eat different types of fish rather than a large amount of one type; and (3) eat smaller fish because some chemicals can build up in fish with age.
What is being done with the information from the study?
OEHHA is further analyzing the data to determine if a more detailed species- and location-specific health advisory is needed for eating fish from San Francisco Bay. The results of this study are also being used by the Regional Water Quality Control Board to focus their pollution control activities. In addition, since this study was designed as a pilot study, the data is being analyzed to determine what additional information is needed in follow up studies.
For More Information
To obtain more information about the fish pilot study, entitled Contaminant Levels in Fish Tissue from San Francisco Bay, or to ask questions, contact:
California Regional Water Quality Control Board
2101 Webster, Street, Suite 500
Oakland, Ca. 94612
(510) 286-1255.
To obtain the fish advisories and health-related information, contact:
Pesticide and Environmental Toxicology Branch of OEHHA
1001 I Street, P.O. Box 4010
Sacramento, CA 95812
(916) 327-7319 or at (510) 622-3170 in Oakland
