SHINER SURFPERCH caught beside the former Hunters Point Naval Shipyard in San Francisco carried more than 10 times the PCBs the state says make a fish unsafe for anyone to eat.
That’s from new testing by the San Francisco Estuary Institute, a 40-year-old nonprofit concerned with the health of the San Francisco Bay and the Sacramento-San Joaquin Delta.
PCBs, or polychlorinated biphenyls, are industrial chemicals that build up in fish fat and can increase the risk of cancer, the state says. The surfperch held about 1,500 to 1,800 parts per billion. A chart the Richmond-based institute presented Oct. 21 puts the state’s no-eating line at about 120. Surfperch from eight other places, including another near Hunters Point, carried about 400 or less.
“Extremely high concentrations at Hunters Point,” the slide says. The shipyard is a federal Superfund toxic cleanup site.
The state already tells everyone not to eat shiner surfperch from the Bay. But a study published Oct. 26 by the institute and the University of Toronto says people who fish for food might keep eating them despite the warnings.
Institute scientist Jennifer Sun presented the results in Berkeley at the annual meeting of the Regional Monitoring Program for water quality in the Bay. The full report hasn’t been released, said Diana Lin, a managing senior scientist at the institute.
The 2024 testing was the program’s ninth round since 1994. Many older pollutants remain above limits, one of Sun’s slides says.
Sun’s chart of mercury in striped bass from the Bay also includes older tests, from 1971 and 1972. The level has stayed about where it was then. “Little change in concentration over 50 years of monitoring,” Sun reports. In 2024, the average striped bass was close to the mercury level at which the state says women 18 to 49 and children should eat none, the chart shows. Too much mercury can harm the brain, especially in fetuses, babies and children, the state says.
Across the Bay, the average shiner surfperch carried about 200 parts per billion of PCBs, also above the no-eating line. In the part of the fish people eat, PCBs “remain high over time,” Sun’s slides say. A second measure adjusts for how fatty each fish is and shows how PCBs are changing in the Bay itself. By that measure, PCBs have fallen about 2.4% a year across the Bay since 1994. “Slow decreases are now detectable,” the slides say, crediting the phasing out of those chemicals.
Toxins declining at a ‘low level’
In a phone interview, Lin said that for PCBs and mercury, “the bad news there is that we’re not seeing declining trends over the last, over a decade.” A closer look at the data may show some low-level declines, she said.
The institute also tested fish for 40 chemicals in a group known as PFAS. It found 21. PFAS is short for per- and polyfluoroalkyl substances. They’re called “forever chemicals” because some don’t break down. Slides Lin presented at the same meeting call them toxic to aquatic life and humans.
“We think PFAS is a concern,” Lin said.
California has no warning about PFAS in fish, although Lin said one is in the works. Until then, the institute uses other states’ limits. The strictest are from Massachusetts.
Plastic is in the fish, too. The Oct. 26 study found microplastic particles in 20 of 25 striped bass fillets from the Bay. It estimated almost four particles in the meat of the average fish. About 70% of the particles in the study were less than 1 millimeter long. Lin said the levels “aren’t higher than other food sources that people eat.”
The state’s advice on fish from San Francisco Bay, updated in 2023, is based on mercury, PCBs and two old pesticides, DDT and dieldrin. It doesn’t cover PFAS or plastic.
Besides shiner surfperch, no one should eat Mississippi silverside, Pacific sardine or topsmelt from the Bay, or any fish from the Lauritzen Channel in Richmond, the state says.
Women 18 to 49 and children 1 to 17 also should not eat sharks, striped bass or white sturgeon. Men, and women 50 and older, can eat one serving a week of those.
The state tells everyone to eat only the skinless fillet, because PCBs build up in the skin, fat and organs.
“From our work with community groups, we have heard anecdotal reports that people do eat other portions of the fish,” Lin said.
‘Culturally appropriate advisories’ recommended
In a study published in February, Biomonitoring California, a state program, tested the blood of Chinese and Vietnamese American adults in the Bay Area in 2016 and 2017. Vietnamese American participants who ate fish they caught three or more times a week had 66% to 125% more of four kinds of PFAS in their blood than those who ate caught fish less than once a month. Vietnamese American participants who ate parts of the fish other than the fillet had 34% to 124% more PFAS in their blood than those who didn’t.
The study calls for “culturally appropriate advisories for seafood consumption.”
The institute plans to test sport fish every three years instead of every five.
In May, the U.S. Environmental Protection Agency picked an institute project called “Protecting Bay Fishers” for funding. It costs about $4 million, about $3 million of it from the EPA. From this fall through 2031, it will collect 1,200 surveys of what people catch and eat, test more kinds of fish in more places and work with fishing communities and tribes to cut their exposure.
The San Francisco Bay Regional Water Quality Control Board is adding $141,000 for surveys of tribal fishing. The board says it will use them to decide where to designate waters in the region for subsistence fishing, or fishing for food.
Lin said she doesn’t know how well current warnings on mercury and PCBs reach people, “but there should be more effort there.”
“For PFAS, I don’t think that that’s been communicated yet,” she said, “because there’s no California threshold yet.”