The fish carried roughly 1,500 to 1,800 parts per billion of polychlorinated biphenyls, or PCBs, compared with the state's no-eating threshold of about 120 parts per billion, according to a chart the Richmond-based nonprofit presented at a Berkeley meeting on Oct. 21. Surfperch from eight other locations, including another site near Hunters Point, contained about 400 parts per billion or less.

"Extremely high concentrations at Hunters Point," the presentation slide stated. The shipyard is a federal Superfund toxic cleanup site.

PCBs are industrial chemicals that accumulate in fish fat and can increase cancer risk, state health officials say. The state already advises everyone not to eat shiner surfperch from San Francisco Bay, but a study published Oct. 26 by the institute and the University of Toronto suggests that people who fish for food may continue to eat them despite the warnings.

Institute scientist Jennifer Sun presented the findings at the annual meeting of the Regional Monitoring Program for water quality in the bay. The full report has not yet 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, according to Sun's presentation.

Mercury levels in striped bass from the bay have shown little change over five decades. Sun's chart, which includes older tests from 1971 and 1972, notes "little change in concentration over 50 years of monitoring." In 2024, the average striped bass was close to the mercury level at which the state says women aged 18 to 49 and children should eat none. Excessive mercury can harm the brain, especially in fetuses, babies, and children.

Across the bay, the average shiner surfperch carried about 200 parts per billion of PCBs, also above the no-eating line. In the portion of the fish people eat, PCBs "remain high over time," Sun's slides said. A second measure that adjusts for fish fattiness shows PCBs have declined about 2.4% per year baywide since 1994, a slow decrease credited to the phasing out of those chemicals.

In a phone interview Thursday, 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 reveal some low-level declines, she added.

The institute also tested fish for 40 chemicals in a group known as PFAS, or perfluoroalkyl and polyfluoroalkyl substances, and found 21. PFAS are called "forever chemicals" because some do not break down. Slides Lin presented at the same meeting describe them as 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 of which are from Massachusetts. By those limits, "almost all of our samples exceed the one meal per day threshold," Lin said. Some fish, especially in the South Bay, had too much to eat even once a week. Largemouth bass averaged about twice the weekly limit.

Plastic is present in the fish as well. The Oct. 26 study found microplastic particles in 20 of 25 striped bass fillets from the bay, estimating almost four particles in the meat of the average fish. About 70% of the particles 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 older pesticides, DDT and dieldrin. It does not cover PFAS or plastic.

Besides shiner surfperch, the state says no one should eat Mississippi silverside, Pacific sardine, or topsmelt from the bay, or any fish from the Lauritzen Channel in Richmond. Women aged 18 to 49 and children aged 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 species.

The state advises 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.

A February study by 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. Those who ate parts of the fish other than the fillet had 34% to 124% more PFAS in their blood. 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 selected an institute project called "Protecting Bay Fishers" for funding. The project costs about $4 million, with about $3 million 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 reduce their exposure. The San Francisco Bay Regional Water Quality Control Board is adding $141,000 for surveys of tribal fishing, which the board says will help decide where to designate waters for subsistence fishing.

Lin said she does not 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."