More than three decades after regulators first flagged chemical contamination in San Francisco Bay fish, new testing shows the problem hasn't gone away. Shiner surfperch collected near Hunters Point Naval Shipyard carried PCB concentrations more than 10 times the state's threshold for unsafe consumption, according to researchers who presented findings at a recent regional water-quality meeting in Berkeley.
The results come from the ninth round of testing since 1994, when the San Francisco Bay Regional Water Quality Control Board first documented the problem in a pilot study, according to the San Francisco Estuary Institute. Jennifer Sun presented the 2024 testing results at the Regional Monitoring Program's annual water-quality meeting in Berkeley, where an institute chart put the state's no-eating PCB threshold at roughly 120 parts per billion. Shiner surfperch caught beside Hunters Point, a federal Superfund toxic cleanup site, contained roughly 1,500 to 1,800 parts per billion of PCBs, while an institute presentation described the concentrations there as extremely high. By comparison, surfperch from eight other Bay locations contained about 400 parts per billion or less, and the Bay-wide average for the species came in around 200 parts per billion.
Mercury Levels Barely Budge in Striped Bass
Mercury tells a similarly stubborn story. Sun reported little change in striped bass mercury concentration over 50 years of monitoring, with levels in 2024 staying close to where they were in tests from 1971 and 1972. The 2024 average for striped bass sat near the threshold at which the state advises women ages 18 to 49 and children to eat none of the fish at all — a serious concern given that mercury can harm the brain, especially in fetuses, babies and young children.
There is some nuance in the PCB picture. Bay PCBs, measured by a fish-fat-adjusted standard, have declined about 2.4% per year since 1994, and Sun's presentation slides said slow decreases are now detectable and credited the phaseout of the chemicals decades ago. Still, Diana Lin of the Estuary Institute said PCBs and mercury have not shown clear declining trends over more than a decade, though she added that a closer review might reveal some low-level declines. Lin also said the full report from the latest round of testing has not yet been released.
PFAS, the Forever Chemicals With No State Warning
Layered on top of the legacy pollutants is a newer worry: PFAS, or perfluoroalkyl and polyfluoroalkyl substances, some of which never break down in the environment and are known as forever chemicals. The Estuary Institute tested Bay fish for 40 PFAS compounds and found 21 of them present, according to meeting slides that described the chemicals as toxic to both aquatic life and humans. Lin called PFAS a genuine concern, but noted that California currently has no fish warning covering the chemicals at all, even as a state advisory is reportedly in development.
In the absence of a state standard, the institute relies on other states' PFAS thresholds, drawing on Massachusetts' limits because they are the strictest available. Per Lin, almost all of the institute's fish samples exceeded the Massachusetts one-meal-per-day threshold, and some samples — especially in the South Bay — exceeded limits for eating the fish even once a week. Largemouth bass averaged about twice the weekly PFAS limit under that benchmark. Separate reporting from the San Francisco Public Press found high PFAS levels in 10 fish species frequently caught in the Bay, based on an institute study of samples collected between 2009 and 2019 that turned up 20 types of forever chemicals, including one the outlet said had never before been detected in marine fish. That same report noted that fillet-based testing may actually underestimate exposure for anglers who eat whole fish or parts like the head.
Local News Matters reported that more than 80% of fish from the southern Bay exceeded the Massachusetts weekly threshold, compared with just 8% elsewhere in the Bay, and that about 91% of samples tested with the most advanced methods contained PFOS specifically. Using the same Massachusetts benchmark, that outlet found 83% of tested fish were considered unsafe to eat daily, and a third weren't considered safe even at half a pound per week.
Microplastics Turn Up in Striped Bass Fillets Too
Contamination concerns extended beyond chemicals in a study published October 26 by the Estuary Institute and the University of Toronto, which examined whether anglers might keep eating Bay fish despite the warnings. That study found microplastic particles in 20 of 25 striped bass fillets tested, estimating almost four particles in the meat of the average fish, with about 70% of those particles measuring less than 1 millimeter long. Lin said microplastic levels in Bay fish are not higher than those found in other foods people commonly eat.
What California's Current Advisory Covers — and What It Doesn't
California's existing fish advice for San Francisco Bay, last updated in 2023, is based on mercury, PCBs, DDT and dieldrin — it does not account for PFAS or plastic contamination at all. The state advises everyone to skip shiner surfperch from the Bay entirely, along with Mississippi silverside, Pacific sardine and topsmelt, and tells anglers not to eat any fish caught from the Lauritzen Channel in Richmond. For sharks, striped bass and white sturgeon, the state advises women ages 18 to 49 and children ages 1 to 17 to avoid them altogether, while allowing men and women 50 and older one serving per week. Everyone is advised to eat only skinless fillets, since PCBs concentrate in skin, fat and organs. Separately, California's Office of Environmental Health Hazard Assessment directs anglers catching American Shad, Chinook Salmon, Striped Bass or White Sturgeon in the Bay to its updated Advisory for Fish that Migrate, and notes that its prior Red Rock Crab guidance was removed while the agency evaluates other contaminants.
Why the Guidance May Not Be Reaching Everyone
Lin said community groups have reported anecdotally that people eat portions of fish beyond the skinless fillet that state guidance targets, and that more effort is needed to communicate current mercury and PCB warnings — while PFAS warnings haven't been communicated at all because California has no threshold to work from. That gap matters most for communities that rely on Bay fish as a dietary staple. A Biomonitoring California study that tested the blood of Bay Area Chinese and Vietnamese American adults in 2016 and 2017 found that Vietnamese American participants who ate caught fish at least three times weekly had 66% to 125% more of four PFAS types in their blood than those who ate caught fish less than monthly. Participants who ate non-fillet portions of fish had 34% to 124% more PFAS in their blood than those who didn't. That study called for culturally appropriate seafood consumption advisories.
New Funding Aims to Fill the Gaps
The Estuary Institute, a 40-year-old nonprofit focused on the Sacramento Delta and San Francisco Bay, plans to shift sport fish testing from once every five years to once every three. The U.S. Environmental Protection Agency selected the institute's Protecting Bay Fishers project for funding in May, a roughly $4 million effort with about $3 million coming from the EPA. The project will test more kinds of fish in more locations, work with fishing communities and tribes to reduce exposure, and collect 1,200 surveys on what people catch and eat between this fall and 2031. The San Francisco Bay Regional Water Quality Control Board is adding $141,000 for surveys of tribal fishing, which it will use to help decide where to designate regional waters for subsistence fishing. As reported by NBC Bay Area, the findings underscore that while some chemicals are slowly declining, many older pollutants remain stubbornly above health thresholds in the fish Bay Area anglers keep pulling from the water.
