What are PCBs in Fish and Why Are They a Concern?

January 11, 2026 •

4 min read

Over one billion pounds of polychlorinated biphenyls (PCBs) were produced in the United States before their ban in 1979. What are PCBs in fish and how do these persistent pollutants continue to pose a threat to both marine ecosystems and human health through the consumption of contaminated seafood? These industrial chemicals, once widespread, persist in the environment and accumulate in the fatty tissues of aquatic organisms, creating long-term risks.

Quick Summary

PCBs are synthetic industrial chemicals that accumulate in the fatty tissues of fish, primarily through sediment exposure and the food chain. This bioaccumulation can lead to significantly higher concentrations in fish than in the surrounding water. They are linked to potential health issues in humans, prompting consumption advisories, particularly for larger and bottom-feeding species. Proper fish preparation can minimize exposure.

Key Points

Origin of PCBs: PCBs are man-made industrial chemicals, banned since 1979, but still present in the environment due to their persistence.
Path of Contamination: PCBs enter water bodies through industrial waste, leaks, and spills, where they bind to sediment.
Bioaccumulation and Biomagnification: Fish absorb PCBs from water and prey, causing levels to build up in their fatty tissues and magnify up the food chain.
High-Risk Fish: Bottom-feeding fish and large predatory species are most likely to have high PCB concentrations.
Health Concerns: Exposure to PCBs can cause health problems in humans, including developmental issues in infants, endocrine disruption, and is classified as a probable carcinogen.
Reducing Exposure: Simple steps like trimming fat, cooking properly, and eating a varied diet can help reduce human exposure to PCBs from fish.

What are PCBs (Polychlorinated Biphenyls)?

PCBs, or polychlorinated biphenyls, are a group of manufactured organic chemicals comprising 209 individual chlorinated compounds called congeners. Prized for their chemical stability, low flammability, and excellent insulating properties, they were widely used in a variety of industrial and commercial products, including electrical transformers, capacitors, hydraulic fluids, and plasticizers. However, their persistent and toxic nature led to a ban on production in the United States in 1979, and globally under the Stockholm Convention. Despite the ban, their resilience means they are still found throughout the global environment in soil, sediment, and water, where they continue to pose a risk to ecosystems.

How Do PCBs Enter the Environment?

The journey of PCBs into aquatic ecosystems is a multi-step process, largely driven by their past widespread use and subsequent improper disposal. Releases occurred through manufacturing processes, leaks from old equipment, spills, and atmospheric deposition. Due to their low water solubility and high lipid solubility, PCBs bind strongly to organic particles and sediment at the bottom of lakes, rivers, and oceans, where they can remain for many years.

The Process of Bioaccumulation and Biomagnification

This binding to sediment is the starting point for PCB contamination in fish. The process occurs in two main ways:

Bioaccumulation: This is the buildup of PCBs in a single organism over its lifetime. As fish absorb PCBs directly from the water through their gills and from contaminated sediments, the concentration within their fatty tissues increases. The concentration in fish can be hundreds of thousands of times higher than in the surrounding water.
Biomagnification: This is the increasing concentration of PCBs in organisms at successive trophic (food chain) levels. When larger predatory fish eat smaller contaminated fish, they inherit and concentrate the PCBs from their prey. This means that older, larger fish and species at the top of the food chain tend to have the highest levels of contamination.

Which Fish are Most at Risk?

The risk of PCB contamination is not uniform across all fish species. Several factors influence how much of the chemical a fish accumulates, including its diet, age, and habitat. As a general rule, fatty fish, bottom feeders, and predatory species tend to have higher concentrations.

Common Fish with Higher PCB Levels:

Bottom Feeders: Species like carp, catfish, and American eel live and feed near the contaminated sediment, increasing their exposure.
Predatory Fish: Larger fish, such as striped bass, pike, and walleye, consume many smaller fish over their lifespan, leading to biomagnification.
Fatty Fish: PCBs are fat-soluble, so fish with higher fat content, such as certain types of farmed salmon, often have higher concentrations.

Comparison: Wild vs. Farmed Salmon PCBs


Feature	Wild-Caught Salmon	Farmed Atlantic Salmon
Dietary Source of PCBs	Mostly from natural forage fish in the ocean environment.	From fish feed pellets made from smaller, processed fish and other ingredients.
PCB Concentration	Generally lower due to feeding on a more varied diet in a broader environment.	Can be significantly higher than wild salmon, primarily influenced by the quality of fish feed.
Source Variation	Varies by ocean region and species, with some Pacific wild salmon having very low levels.	Varies by farm location and feed source, with some regions historically having higher concentrations.
Recommendations	Generally considered a safe, healthy choice with low exposure risk.	Advisories may recommend more limited consumption for sensitive populations, depending on source.

Potential Health Effects in Humans

Ingesting PCB-contaminated fish is the primary route of human exposure. Because PCBs are stored in fatty tissue and are eliminated slowly from the body, they can accumulate over many years, potentially causing adverse health effects. While the scientific community continues to research the full extent of the risks, several potential health issues have been identified.

Carcinogenic and Non-Carcinogenic Risks

Cancer: The U.S. Environmental Protection Agency (EPA) has classified PCBs as probable human carcinogens. The International Agency for Research on Cancer has also determined that PCBs are carcinogenic to humans.
Reproductive and Developmental Effects: Studies have linked high PCB exposure in pregnant women to lower birth weights and developmental issues in their infants, including impaired motor skills and memory problems.
Neurological Effects: High levels of PCBs can harm the developing fetus and infant, impacting neurological development and learning.
Endocrine Disruption: PCBs can interfere with the body's endocrine system, potentially affecting hormone levels, particularly thyroid hormones which are critical for development.
Immune System Effects: Some studies have shown that PCBs can suppress the immune system in animals, potentially increasing susceptibility to certain infections and illnesses.

Reducing Your Exposure to PCBs

For most people, the benefits of eating fish—a key source of protein and omega-3 fatty acids—outweigh the risks of PCB exposure, provided they follow consumption guidelines. However, sensitive populations like children, pregnant women, and breastfeeding mothers should be more cautious and follow local fish consumption advisories.

Simple preparation techniques can also significantly reduce your exposure:

Trim the Fat: Since PCBs accumulate in fat, removing the skin and visible fatty areas (belly, top back, and dark meat along the side) from fish fillets can help.
Use Healthy Cooking Methods: Grilling, baking, or broiling fish on an elevated rack allows the fat to drip away. Avoid frying, which seals in chemical pollutants.
Vary Your Diet: Eating a variety of fish from different sources limits your exposure to any single contaminant.

Conclusion

PCBs in fish remain a persistent environmental issue long after their production was banned, due to their chemical stability and ability to bioaccumulate and biomagnify through aquatic food webs. Consumers can minimize their exposure by being aware of the risks, following local fish consumption advisories, and using proper preparation techniques. By staying informed about the sources and risks associated with PCBs, individuals can continue to enjoy the health benefits of seafood while making safer, more conscious dietary choices.

Further Research

For authoritative information and specific consumption guidelines, consult local environmental and health agencies. A valuable resource for broader information and health impacts is the EPA's page on PCBs.

Learn about Polychlorinated Biphenyls | US EPA

Frequently Asked Questions

PCBs, or polychlorinated biphenyls, are synthetic industrial chemicals that accumulate in the fatty tissue of fish over their lifetime through a process called bioaccumulation.

PCBs entered water systems from industrial manufacturing, spills, and improper disposal before their ban in 1979. They settle into river and lake sediments, where they are taken up by small organisms and fish.

Fish with higher fat content, larger predatory fish, and bottom-feeding species, like wild striped bass, farmed salmon, and catfish, generally have the highest PCB concentrations due to biomagnification.

Cooking does not destroy PCBs. However, using methods that allow fat to drip away, such as baking, broiling, or grilling on a rack, can help reduce the amount of PCBs consumed.

High-level exposure to PCBs has been linked to health problems, including potential cancer, developmental issues in infants, and effects on the endocrine and immune systems. For most people, following fish consumption advisories is the best way to minimize risk.

Bioaccumulation is the buildup of a substance, like PCBs, in an organism over its lifetime. Biomagnification is the increasing concentration of a substance as it moves up the food chain from smaller organisms to larger predators.

Pregnant women, breastfeeding mothers, children, and people who eat large amounts of locally caught fish are considered most at risk and should pay close attention to consumption advisories.

Yes. PCBs can be transferred from a mother to her unborn baby during pregnancy. Additionally, PCBs are stored in fat and can be present in breast milk, meaning exposure can occur during breastfeeding.

Federal and state agencies, like the FDA and EPA, set guidelines and advisories for safe fish consumption based on PCB levels to help people reduce their risk. Checking local advisories for fish caught in specific waters is important.