Estuary News

June 2021

Bay Fish Still Not Good Eating

After decades of efforts to clean up San Francisco Bay, its fish still carry a toxic load that makes them unfit for human consumption. A new Regional Monitoring Program (RMP) report on its 2019 sport fish survey contains some positive news: an overall decline in polybrominated diphenyl ethers (PBDE), hopeful trends in polychlorinated biphenyls (PCBs) and dioxin, and continued low selenium levels. But no downward trend was found for mercury. Then there are per- and polyfluoroalkyl substances (PFAS), which the RMP only began monitoring in 2009 and for which no human consumption advisory levels have been established in California. These chemicals, used in stainproofing, waterproofing, and many other applications, are a new cause for concern.

The 2019 survey was the eighth iteration since 1997, with surveys currently occurring on a five-year cycle. Tissue samples are taken from five core indicator species (striped bass, white sturgeon, shiner surfperch, white croaker, and jacksmelt) selected as most popular for consumption. Supplemental samples from several other species are also analyzed for contaminants. The fish were caught at 13 Bay locations representing popular fishing sites, taken by hook and line, with gill nets and otter trawls, and, in the case of the reclusive monkeyface prickleback, by poke poling.

Monkeyface prickleback.

“The single most significant finding may be the mercury results,” says Jay Davis, co-director of the San Francisco Estuary Institute (SFEI)’s Clean Water Program. “It’s remarkable how flat the concentrations are over a 50-year period.” Mercury is the primary focus of the fish consumption advisories issued by the state Office of Environmental Health Hazard Assessment (OEHHA), a division of the California Environmental Protection Agency.

Davis says legacy mercury from the 19th-century mining era is augmented by atmospheric mercury that’s deposited in the Bay and trapped in sediment. Mercury in striped bass, the main indicator species, is “right on the threshold for no consumption by sensitive populations,” meaning women ages 18 to 49 and children up to 17. He notes that stripers in the Bay have higher mercury levels than those off the East Coast and in the Gulf of Mexico.

Mercury concentrations in striped bass. Source: RMP

The most encouraging trend Davis seesconcerns the flame-retardant PBDEs, showing a sharp decline following manufacturing phaseouts. If that continues, the chemicals may no longer need to be monitored. Dioxin and PCBs appear to be declining at least in white croaker, an important sentinel species because of its high fat content and its mobility within the Bay. Selenium results were amplified by an anomalously high reading in one individual white sturgeon. 

The highest levels of another huge class of multi-use chemicals, PFAS, were found in the South Bay, particularly in largemouth bass from Artesian Slough. The survey found levels exceeding thresholds for human consumption set by states other than California.  According to Davis, the Bay is still ahead of the curve: “We have the most comprehensive monitoring program for PFAS anywhere.” OEHHA deputy director Sam Delson says the agency has PFAS contamination in its sights as well: “We are currently evaluating the toxicity of PFAS chemicals and may be able to develop ATLs (advisory tissue levels) for one or more PFAS chemicals as we complete the evaluations.” The first step may involve interim fish consumption advice for hotspots like Artesian Slough.

RMP scientists found one particular kind of PFAS that has already been banned, perfluorooctane sulfonate (PFOS), prevalent in the Bay fish samples. High PFOS concentrations have also been found in harbor seals and double-crested cormorant eggs in the South Bay. These chemicals, implicated in several kinds of cancer and developmental abnormalities, accumulate in food webs. Eleven states have PFOS fish tissue advisory thresholds in place.

PFAS chemicals in general remain ubiquitous — used in food packaging, waterproofing and stainproofing, Teflon manufacturing, fire-suppression foams, lithium-ion batteries, insecticides, cosmetics, medical inhalers, and ski wax — and are difficult to remove from wastewater.

Map of sampling locations. PMU refers to priority margin unit (sampled in bay margins in special study on PCBs). Source: RMP

Beyond mercury, selenium, dioxin, PCBs, PBDEs, and PFAS, what else is lurking in the Bay? Rebecca Sutton, who heads SFEI’s emerging contaminants program, says nontargeted analysis may augment the traditional way of screening for specific substances: “You take a sample, detect as many chemical signals as possible, and match them up based on a library of standards. You might find some surprises.” The technique has been used on water samples (see “Match Points in Stormwater Soup,” September 2020) and could be applied to fish tissue.

Efforts to keep contaminants out of the Bay encounter the effective limits of regulation. When the use of PBDEs as flame retardants was phased out, manufacturers replaced them with brominated and phosphate-based chemicals that are also toxic; Sutton calls it “a regrettable substitution.” Likewise, some newer PFAS chemicals used in place of older formulations known to be harmful have turned out to be similar in toxicity and persistence, and may be used in greater quantities because they’re less effective. “There’s a whole slew of contaminants out there,” says San Francisco Baykeeper staff scientist Ian Wren. “It’s a whack-a-mole thing.”

PBDE concentrations (PBDEs are derived from flame retardents, now banned) in years where they are significantly different from each other (A-BC). Source: RMP

World trade amplifies the toxic impact: while the U.S., Canada, the European Union, and Japan phased out PFOS, China, India, and Brazil ramped up production. Many of the resulting goods have entered the U.S., and the Bay Area’s waste stream. Atmospheric mercury from coal burned in Asia is deposited in the Bay’s water.

Wren sees the persistence of problematic mercury levels, as well as PCBs (which have declined in some fish species but not as much as anticipated), as evidence of a failed regulatory strategy: “Since the beginning of the RMP in the early 1990s, water quality has remained relatively stagnant. That puts into question the wait-and-see approach pursued by water quality regulators.” The Bay’s tides and currents don’t appear to be flushing contaminants out, especially in the relatively shallow South Bay. Monitoring has identified persistent hotspots. “Why aren’t we cleaning up the contaminated sediment?” he asks. “It would go a long way toward improving the health of the overall Bay.”

Wren points to successful sediment cleanup campaigns in other coastal regions. He acknowledges such efforts would be expensive, and compelling polluters to pay would be difficult; some of the responsible parties are long gone. “Small groups like Baykeeper don’t have the resources to pursue enforcement actions,” he adds. And he feels regulatory agencies lack the political will.

The human risks are no abstraction. Subsistence fishing is a fact of life for many Bay Area residents, particularly among communities of color, the economically disadvantaged, and the homeless. It’s culturally important for some, a stress reliever for others. Some fishers may be unable to read posted warnings about fish consumption or too hungry to observe them.

Davis says there are anecdotal observations suggesting subsistence fishing increased during the pandemic, but no hard data. To get a handle on who’s eating fish from the Bay, the North Bay environmental justice organization All Positives Possible has surveyed fishers in Carquinez Strait as a pilot project, and hopes to expand it. Ensuring that locally caught fish is safe to eat is an essential first step toward restoring a healthy fishery in San Francisco Bay.

Top Film: Fishing off the East Bay waterfront by Sierra Garcia

Prior RMP Stories in Estuary

Sportfish Report, RMP

About the author

Joe Eaton writes about endangered and invasive species, climate and ecosystem science, environmental history, and water issues for ESTUARY. He is also "a semi-obsessive birder" whose pursuit of rarities has taken him to many of California's shores, wetlands, and sewage plants.

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