PCBs in San Diego Bay: The Monsanto Lawsuits, Health Risks, and How to Eat Local Fish Safely

In March 2015, the City of San Diego and the San Diego Unified Port District filed a lawsuit against Monsanto over chemicals that had been banned for more than 35 years. The chemicals were polychlorinated biphenyls, or PCBs, and they were still in the sediments of San Diego Bay and in the tissues of its fish. The suit was the first of its kind in the country and was soon followed by cities, counties, ports, school districts, and states from Seattle to Baltimore. Collectively, those cases have produced some of the largest environmental settlements in U.S. history.

This article explains what PCBs are, how they ended up in San Diego Bay and other waterways, what happened in the San Diego case and the wave of litigation that followed, what is known about PCBs and human health, and what people who eat fish from contaminated waters can do to reduce their exposure.

What PCBs Are

PCBs are a family of 209 related synthetic chemicals made by attaching chlorine atoms to a pair of linked benzene rings. According to the U.S. Environmental Protection Agency, they were manufactured in the United States from 1929 until their manufacture and import were banned in 1979, because of mounting evidence of their toxicity. Their non-flammability, chemical stability, high boiling point, and electrical insulating properties made them useful in hundreds of industrial and commercial applications.

They were used as coolants and insulating fluids in transformers and capacitors, in hydraulic systems, as plasticizers in paints, caulks, and sealants, in fluorescent light ballasts, and in carbonless copy paper. The same stability that made them useful makes them a lasting problem: PCBs break down very slowly, bind to sediments and soils, travel long distances, and accumulate in the fatty tissues of animals. Concentrations increase at each step up the food chain, so large predatory fish, marine mammals, and people who eat them can carry much higher levels than the water around them.

Monsanto was the dominant producer. The company acquired the original U.S. manufacturer in the 1930s and remained the only North American producer of PCBs until it stopped production in 1977, shortly before the federal ban took effect under the Toxic Substances Control Act.

How PCBs Were Recognized as a Global Pollutant

For their first three decades, PCBs were viewed mainly as useful industrial chemicals. Concern about workers came early, with reports of skin conditions such as chloracne among people who handled them. Recognition of PCBs as a widespread environmental contaminant came in 1966, when Swedish chemist Sören Jensen, while analyzing wildlife samples for the pesticide DDT, identified unknown chlorinated compounds as PCBs. He found them in fish, birds, and other animals, including in samples collected far from industrial sources.

The discovery changed how scientists understood industrial pollution. It showed that chemicals released in one place could spread globally and concentrate in wildlife. Over the following decade, reports accumulated of PCBs in fish, birds of prey, and human breast milk, and of reproductive problems in wildlife. The Japanese cooking oil poisoning of 1968 added evidence of toxicity in people. By the mid-1970s, public and regulatory pressure had grown, leading to the end of U.S. production and the federal ban.

How PCBs Reached San Diego Bay

San Diego Bay has been a hub for shipbuilding, ship repair, and naval operations for more than a century. PCBs were used in paints, electrical equipment, and hydraulic fluids on ships and at shipyards and industrial sites around the bay. Over decades, PCBs from those uses washed into the bay through stormwater drains, spills, and direct discharges, settling into sediments near the shipyards and elsewhere.

State regulators identified contaminated sediments along the shipyard waterfront and ordered cleanup, and dredging and remediation projects removed large volumes of contaminated material. PCBs have been found in bay sediments, water, and the tissue of fish and other marine life. The California Office of Environmental Health Hazard Assessment publishes a fish consumption advisory for San Diego Bay with species-specific recommendations on how often it is safe to eat fish caught there, reflecting contaminants including PCBs.

The companies that used PCBs, discharged them, or operated contaminated sites have borne much of the cleanup cost under state and federal environmental laws. The 2015 lawsuit sought to reach further up the chain, to the manufacturer.

The 2015 Lawsuit

As NBC 7 San Diego reported, the city and the Port sued Monsanto, along with its spin-off Solutia and Pharmacia, the corporate successor to part of the old Monsanto, in federal court. The complaint alleged that Monsanto knew PCBs were toxic and would escape into the environment, yet continued to manufacture and promote them for industrial uses including shipbuilding, electrical components, and paint. The legal theory was public nuisance: that by producing and marketing PCBs while concealing their hazards, Monsanto was responsible for the resulting contamination of a public resource.

Monsanto rejected the claims. The company said it had sold a lawful and useful product that was incorporated by third parties, including the U.S. Navy, into other products, and that if improper disposal caused contamination, those third parties should bear responsibility. Bayer, which acquired Monsanto in 2018, later said the lawsuit had no merit because none of the defendants used, stored, or discharged PCBs in the San Diego Bay environment.

The case moved slowly. Courthouse News reported that a federal judge granted Monsanto’s motion for summary judgment against the City of San Diego, finding the city had not shown that PCBs in its storm drain system directly caused cleanup costs it incurred, while narrowing but allowing the Port District’s claims to proceed.

The Port’s claims were ultimately resolved as part of a national settlement. According to the Port’s outside counsel, Kelley Drye, the Port’s 2015 case was the first of its kind, and the many similar suits that followed led to a class action settlement for local governments approved in November 2022 of approximately $550 million, to be allocated among the Port and other class members. The Port dismissed its individual case in February 2023. The firm noted that San Diego Bay is widely recognized as cleaner than when the Port was established, thanks to decades of cleanup work.

A National Wave of PCB Litigation

San Diego’s suit opened the door for others. Over the following years, cities including Seattle, Portland, Oakland, San Jose, Berkeley, Long Beach, Spokane, and Baltimore brought similar claims, as did several states and many other local governments. Most relied on public nuisance and product liability theories, arguing that Monsanto should pay a share of the enormous cost of cleaning PCBs from stormwater systems, rivers, and bays.

Plaintiffs in these cases have pointed to internal company documents from the late 1960s, produced in litigation, which they say show Monsanto knew PCBs were accumulating in the environment and harming wildlife while continuing to sell them. Monsanto and later Bayer have argued that the company acted lawfully, that it responded to emerging science by restricting sales and ultimately ending production before the federal ban, and that responsibility for releases lies with the users and dischargers.

In 2020, Bayer announced it would pay about $650 million to resolve claims by a nationwide class of local governments, along with separate amounts to resolve claims by several states. After a federal judge raised concerns about the proposed terms, the class agreement was restructured, and a settlement of about $550 million was approved in 2022. Several states pursued their own cases; Oregon, for example, announced a settlement with Monsanto in 2022 of roughly $700 million, among the largest environmental settlements in the state’s history. Other lawsuits have involved schools, where teachers, students, and parents alleged illness from PCBs in old light fixtures and building materials, leading to substantial jury verdicts in some cases.

These cases have not been uniformly successful for plaintiffs. Courts have dismissed some claims, narrowed others, and debated whether a manufacturer can be held liable for nuisance created by how its customers used and disposed of a product decades ago. The legal landscape continues to evolve.

Anniston: the community next to the plant

The most direct human toll of PCB manufacturing occurred in Anniston, Alabama, where Monsanto operated a PCB plant for decades. Residents living near the plant had some of the highest PCB exposures ever measured in a U.S. community. In 2003, Monsanto and Solutia agreed to a settlement of about $700 million with thousands of Anniston residents, and the area became the focus of long-term health studies and EPA cleanup. Anniston remains a reference point in discussions of corporate responsibility for toxic chemicals.

PCBs and Human Health

PCBs are among the most studied environmental contaminants. The evidence comes from occupational studies of workers who made or handled PCBs, from mass poisoning incidents, from communities near contaminated sites, and from large populations with background exposure.

Cancer. In 2013, a working group of the International Agency for Research on Cancer classified PCBs as carcinogenic to humans (Group 1), the agency’s highest category. It found sufficient evidence in humans for malignant melanoma, and limited evidence for non-Hodgkin lymphoma and breast cancer. Dioxin-like PCBs, a subset that act through the same biological pathway as dioxins, were also classified as Group 1.

Development and cognition. Studies of children exposed before birth, including in communities that ate large amounts of contaminated fish, have linked higher prenatal PCB exposure to lower birth weight and to subtle deficits in cognitive development, memory, and attention. Because PCBs cross the placenta and pass into breast milk, pregnant and breastfeeding people and young children are the focus of most advisories.

Mass poisonings. Two incidents in Asia, in Japan in 1968 and Taiwan in 1979, in which cooking oil was contaminated with PCBs and related compounds, caused skin lesions, immune and reproductive effects, and developmental problems in children born to exposed mothers. These events provided some of the clearest evidence of PCB toxicity at high doses.

Immune, endocrine, and other effects. PCBs can affect immune function, thyroid hormones, and reproductive health, and have been associated with liver effects and elevated blood pressure in some studies.

For most people today, exposure is far lower than in those incidents, and background levels in the U.S. population have declined substantially since the ban. The main ongoing concern is people who regularly eat fish from contaminated waters, along with people in older buildings with PCB-containing materials.

Where People Encounter PCBs Today

Fish and seafood. Diet is the main source for most people, especially fatty fish from contaminated lakes, rivers, and bays. Subsistence and recreational anglers who eat their own catch frequently can have much higher exposure than people who buy commercially sold fish.

Old buildings. Buildings constructed or renovated between about 1950 and 1979 may contain PCBs in caulk, paint, and fluorescent light ballasts, which EPA lists among products that may contain PCBs. Schools from that era have been a particular focus, since deteriorating materials can release PCBs into indoor air and dust.

Contaminated sites. Former industrial areas, landfills, and sites where PCB equipment was used or disposed of can continue to release PCBs into soil and water.

Old electrical equipment. Some older transformers and capacitors still in service or improperly stored contain PCB fluids.

Why PCBs Persist and Travel

PCBs were designed to be stable, and chemically they are. The carbon-chlorine bonds that give them resistance to heat and fire also make them resistant to breakdown by sunlight, water, and microbes. In sediments, PCBs can remain for decades. Heavily chlorinated forms are the most persistent.

They also move. PCBs can evaporate from soil and water, travel through the atmosphere, and settle far from where they were used, which is why they are found in Arctic wildlife and in remote lakes. In water, they attach to particles and settle into sediments, where bottom-dwelling organisms take them up. From there they move up the food web: small organisms are eaten by fish, fish by larger fish, birds, marine mammals, and people. At each step, PCBs accumulate in fat faster than they are eliminated, a process called biomagnification.

That is why fish advisories focus on larger, older, fattier, and predatory fish, and why the parts of the fish where fat concentrates carry most of the PCBs.

What the Settlement Money Pays For

Settlements from the municipal PCB cases are distributed to participating cities, counties, ports, and other entities according to formulas that account for factors such as population and the extent of stormwater systems. The money is generally intended to help pay for PCB-related work, including stormwater treatment, sediment cleanup, monitoring, and compliance with water quality requirements that limit PCB discharges.

Those costs are large. Many older cities are under regulatory requirements to reduce PCBs flowing through their storm drains into impaired water bodies, which can require identifying and removing legacy sources in old buildings and industrial areas, installing treatment systems, and dredging contaminated sediments. Settlement funds cover only a portion of these long-term costs, which continue to fall mainly on ratepayers and local governments.

From PCBs to PFAS: A Familiar Pattern

The legal strategy San Diego pioneered against Monsanto has become a template for litigation over other persistent chemicals. Water utilities, states, and local governments have sued manufacturers of PFAS, the per- and polyfluoroalkyl substances used in nonstick coatings, stain-resistant fabrics, and firefighting foam, using similar public nuisance and product liability theories. Several of those cases have produced settlements in the billions of dollars.

The parallels are striking. Both classes of chemicals were valued for their durability, used widely for decades, and found years later to persist in the environment and in people. Both have prompted questions about what manufacturers knew and when, and about who should pay to clean up contamination that is spread across entire regions. The PCB experience suggests that such cleanups take decades and that litigation, while it can shift some costs, does not substitute for preventing persistent chemicals from being released in the first place.

PCBs in Schools: What Parents Should Know

Schools built or renovated between about 1950 and 1979 may contain PCBs in window caulk, paint, and older fluorescent light fixtures. As these materials age, PCBs can migrate into indoor air, dust, and nearby surfaces. Leaking or failing light ballasts can release PCB-containing oil. Concern about school buildings has grown after lawsuits by teachers and families who alleged illness from exposure in older schools.

EPA has long recommended that schools replace old fluorescent light ballasts that may contain PCBs, and that building managers identify and safely remove PCB-containing caulk during renovations, following federal rules for handling PCB waste. Measures such as improved ventilation and thorough cleaning can reduce exposure while longer-term removal is planned.

Parents who are concerned can ask their school district when buildings were constructed or renovated, whether light fixtures have been replaced, whether any testing for PCBs in caulk or air has been done, and what the district’s plan is for older buildings. Renovation of older buildings should always follow proper procedures, since disturbing caulk or paint without precautions can release more PCBs.

How Contaminated Waterways Are Cleaned Up

Removing PCBs from bays and rivers is technically difficult, because the chemicals are bound to sediments spread across large areas. Cleanup plans typically combine several approaches.

Dredging removes contaminated sediment, which is then dewatered and disposed of in secure landfills. It is effective for concentrated hot spots but expensive and can temporarily stir up contaminants.

Capping covers contaminated sediment with clean sand, gravel, or engineered materials, isolating it from the water and from organisms that live in the sediment. Caps must be monitored to ensure they remain intact.

Monitored natural recovery relies on cleaner sediment gradually burying contaminated layers, combined with long-term monitoring of sediment and fish. It is used where contamination is lower or where active cleanup would cause more harm than good.

Source control stops new PCBs from reaching the water, for example by cleaning storm drains, removing contaminated soil from upland sites, and treating stormwater. Without source control, sediment cleanups can be recontaminated.

San Diego Bay’s shipyard cleanup used dredging of the most contaminated sediments along with other measures, and regulators continue to monitor results. Across the country, large cleanups have taken decades from discovery to completion.

Don’t Give Up on Fish

PCB advisories can leave the impression that fish should be avoided altogether. Health agencies say the opposite. Fish is a valuable source of protein, omega-3 fatty acids, iodine, selenium, and vitamin D, and the FDA and EPA’s joint advice on eating fish encourages most adults, and pregnant and breastfeeding people, to eat fish regularly while choosing lower-contaminant options.

The distinction is between commercially sold fish, most of which is low in PCBs and mercury, and fish caught repeatedly from specific contaminated waters. The risk from PCBs is concentrated among people who frequently eat their own catch from places like urban bays, industrial rivers, and certain lakes, and who eat the fattier parts of the fish. For them, following the local advisory is the single most important step.

Situation	PCB concern	What to do
Store-bought fish, eaten a few times a week	Low	Follow FDA/EPA “best choices” guidance; vary species
Occasional recreational catch from an advisory area	Moderate	Check the advisory; choose recommended species; trim fat and skin
Frequent subsistence fishing in contaminated waters	High	Strictly follow species limits; favor less-contaminated species and locations
Pregnant, breastfeeding, or feeding young children	Higher sensitivity	Use the stricter advisory category; prioritize low-contaminant fish

Who Carries the Highest Exposure Today

PCB exposure is not evenly distributed. People who regularly eat fish they catch themselves from urban bays and industrial rivers, often for cultural reasons or because fishing provides an affordable source of protein, can have much higher intake than the general population. In many coastal and river cities, these subsistence anglers are disproportionately from immigrant, Indigenous, and low-income communities. Studies of angler communities in several U.S. regions have found that advisories do not always reach them, especially when materials are available only in English or posted only online.

Public health agencies have responded with multilingual signs at piers, community outreach through local organizations, and advice that emphasizes which species and parts of the fish are safer rather than simply telling people to stop fishing. The goal is to keep the nutritional and cultural benefits of fishing while reducing contaminant exposure.

Workers who handle old electrical equipment, demolish or renovate older buildings, or work at contaminated sites can also face elevated exposure and should follow workplace protections for PCB-containing materials.

How to Find Your Local Fish Advisory

Every state issues fish consumption advisories for water bodies with elevated contaminants. In California, the Office of Environmental Health Hazard Assessment maintains advisories for San Diego Bay and many other locations, with recommended maximum servings per week for specific species. Other states publish similar guidance through health or environmental agencies. Advisories are often posted at piers and boat launches, sometimes in several languages, since many subsistence anglers speak languages other than English.

When reading an advisory, look for three things: which species are covered, how many servings per week or month are recommended, and whether separate, stricter limits apply to women of childbearing age and children. A “do not eat” listing for a particular species means that species should be avoided entirely from that location.

Cleanup Progress and What Remains

San Diego Bay today is cleaner than it was decades ago. Sediment remediation at shipyard sites, stormwater controls, and restrictions on industrial discharges have reduced contamination, and the Port and regional water quality regulators continue monitoring. Nationally, PCB levels in the environment and in human blood have declined since the 1979 ban.

But PCBs have not gone away. They remain in sediments, in older buildings, in landfills, and in the global environment, where they cycle through air and water and continue to accumulate in wildlife. Cleaning up contaminated waterways is slow and expensive; major river and harbor cleanups have taken decades and cost billions of dollars. Stormwater systems in older cities continue to carry PCBs from legacy sources into waterways, which is why local governments have pursued the manufacturer to help cover costs.

The settlement money from the PCB litigation is being distributed to cities, ports, and states to support stormwater treatment, sediment cleanup, and monitoring. How effectively that money is spent will determine how much the settlements translate into cleaner water.

The Broader Lesson

The PCB story is often cited as a case study in how chemicals that seemed ideal for industry can create long-lasting environmental and health problems. PCBs were valued precisely because they did not break down, and that same property is why they are still in San Diego Bay decades after production ended.

It is also a case study in who pays. Under environmental cleanup laws, the users and dischargers of PCBs, including shipyards, utilities, and the military, have borne much of the direct cleanup cost. The municipal lawsuits sought to shift part of that burden to the manufacturer on the theory that it knew about the risks. The settlements suggest that the manufacturer’s successor judged it better to pay than to keep litigating, without admitting liability.

Similar debates now surround other persistent chemicals, most notably PFAS, the so-called forever chemicals, where local governments and water utilities are pursuing manufacturers under legal theories that echo the PCB cases.

Frequently Asked Questions

Why did San Diego sue Monsanto?

In 2015, the City of San Diego and the Port of San Diego sued Monsanto, alleging it knowingly manufactured and promoted toxic PCBs that contaminated San Diego Bay, and seeking cleanup costs and damages under a public nuisance theory.

How was the San Diego case resolved?

A federal judge granted Monsanto summary judgment against the city’s claims while allowing the Port’s narrowed claims to proceed. The Port later resolved its claims through a national class settlement for local governments of about $550 million, approved in 2022, and dismissed its individual case in 2023.

Are PCBs still a health risk?

Yes, mainly for people who frequently eat fish from contaminated waters and for occupants of older buildings with deteriorating PCB-containing materials. IARC classifies PCBs as carcinogenic to humans, and prenatal exposure has been linked to developmental effects.

Is it safe to eat fish from San Diego Bay?

California’s OEHHA publishes a San Diego Bay advisory with species-specific recommendations. Follow those limits, choose recommended species, and trim fat and skin before cooking.

When were PCBs banned?

U.S. manufacture and import of PCBs were banned in 1979 under the Toxic Substances Control Act. Monsanto stopped production in 1977.

Do PCBs build up in the body?

Yes. PCBs are stored in body fat and are eliminated slowly, over years. Levels reflect long-term exposure, which is why reducing intake from contaminated fish over time matters more than any single meal.

Can PCBs pass to babies?

PCBs cross the placenta and pass into breast milk. Health agencies still recommend breastfeeding for its many benefits, while advising pregnant and breastfeeding people to follow stricter fish advisory limits to reduce their own PCB intake.

Are store-bought fish high in PCBs?

Most commercially sold fish are low in PCBs. The main concern is fish caught frequently from specific contaminated waters covered by local advisories.

Who pays for PCB cleanup?

Under environmental laws, the parties that used, discharged, or disposed of PCBs at a site bear much of the direct cleanup cost. Settlements with Monsanto’s successor provide additional funds to many local governments, but ratepayers and public agencies still carry most long-term stormwater and cleanup costs.

References

1. U.S. Environmental Protection Agency. Learn about Polychlorinated Biphenyls (PCBs). epa.gov
2. U.S. Environmental Protection Agency. Policy and Guidance for Polychlorinated Biphenyls (PCBs). epa.gov
3. Lauby-Secretan B, Loomis D, Grosse Y, et al. Carcinogenicity of polychlorinated biphenyls and polybrominated biphenyls. Lancet Oncology. 2013;14(4):287–288. PMID 23499544
4. NBC 7 San Diego. City of San Diego Sues Monsanto Over PCB Pollution. 2015. nbcsandiego.com
5. Courthouse News Service. Monsanto can’t dodge SoCal port’s pollution case. courthousenews.com
6. Kelley Drye & Warren. Port of San Diego Reaches Settlement in Monsanto PCB Case. February 7, 2023. kelleydrye.com
7. California Office of Environmental Health Hazard Assessment. San Diego Bay fish advisory. oehha.ca.gov
8. U.S. Food and Drug Administration and U.S. EPA. Advice about Eating Fish. fda.gov

Last updated: September 26, 2026