Marine Toxins: What’s In Your Seafood?

By Delialah Falcon. May 7th 2016

Toxins that are found in seafood are known as marine toxins. Marine toxins are chemicals that occur in the environment and can contaminate some varieties of seafood. It is nearly impossible for individuals to be able to detect marine toxins in seafood by simply looking or smelling them, as contaminated seafood looks and smells normal. Marine toxins cannot be detected by taste either. While mercury content is one thing to consider when eating seafood, marine toxins are a whole other issue.

Of all of the seafood that is consumed in America, roughly 80 percent of it is imported from overseas. Some recent studies have shown that much of that seafood may be contaminated with marine toxins that can lead to the development of serious health conditions. The seafood that most commonly tests positive for contamination is imported from China, Taiwan, Vietnam, Indonesia and Malaysia, and includes:

  • Shrimp
  • Catfish
  • Crabmeat
  • Tilapia

Polychlorinated Biphenyl (PCB)

PCB’s are dangerous neurotoxins that have been banned in the United States. Even after 20 years of removing them from manufactured products in an attempt to rid the environment of them, PCB’s continue to be detected in human blood samples and breast milk. Studies conducted by the Environmental Working Group found that 7 out of 10 farmed salmon available in Washington DC and Portland, Oregon grocery stores were contaminated with PCB’s. According to this study, researchers conclude that farmed salmon generally contain the highest level of PCB’s of all protein sources in the American food supply, higher than that found in beef, wild salmon and other types of seafood. The problem may lie in the fact that farmed salmon are fed fishmeal that is made from a high percentage of fish oil and ground-up smaller fish, both of which often contain significant amounts of PCB’s.

Flame Retardants

Flame retardants are considered by many scientists and researchers to be the next toxin that is equally dangerous to PCB’s. They are commonly found in common household equipment, such as televisions, computers and furniture. They are neurotoxic chemicals that can be quite harmful.

Flame retardants, also known as PBDE’s (polybrominated diphenyl ethers), are unregulated by American state and federal authorities. Some other governments, such as the European Union, have banned certain flame retardants because of their potential to cause health problems. Analysis of domestic-grown fish have found that at least six common species have tested positive for contamination with flame retardants.

Chlorinated Dioxins

Dioxins are a byproduct of industrial processes. They are chemical compounds that sometimes occur through natural processes, such as forest fires. They are present in low levels in the diet. However, they can be present in moderate amounts in contaminated seafood.


Pesticides that are commonly used for agriculture often contaminate seafood. These pesticides may accumulate in seafood in high amounts, enough to cause illness in individuals who consume enough of the contaminated fish. Although illnesses have been reported in individuals after consuming only one pesticide-contaminated seafood meal, it is a very rare occurrence.

Generally, the hazard is greatest among individuals who experience long-term exposure to pesticide-contaminated seafood. Seafood that is found in the open ocean has a lower risk of being contaminated with pesticides. Higher risk is found in fish that are caught in near-shore coastal waters, estuaries, fresh water and possibly those caught near aquaculture operations.


Crude oil that leaks into the ocean has been found to contain elevated levels of at least 6 toxic chemicals. These chemicals have been linked to health concerns, specifically kidney damage and cancer. Studies have found elevated levels of crude oil present in some types of seafood.


Arsenics is an element that is found naturally in soil and minerals. It is a very common element that is widely distributed and therefore, often shows up in seafood. Seafood is one of the main factors that leads to arsenic consumption in the diet. Arsenic, though natural, is toxic. Even very low levels of arsenic in the body can lead to the development of numerous health problems. If arsenic reaches high levels in the body, it can be fatal.


Melamine is an industrial chemical that is found in plastics and fertilizers. Recent reports state that manufacturers of fish feed in China regularly add melamine to the feed. The chemical accumulated in the fish that consume the contaminated fish feed. Currently, there are no guidelines from the Food and Drug Administration that require testing for melamine in imported seafood.


BMAA (beta-Methylamino-L-alanine) is a compound that comes from blue-green algae known as cyanobacteria. This type of bacteria is found in the ocean, lakes and soil. When fish and other aquatic creatures consume BMAA, it accumulates in their bodies. This results in contaminated seafood.

Why Are These Toxins Dangerous

All of these toxins can lead to varying degrees of illness and health conditions. Health problems that can develop as a result of consuming marine toxins range from mild to life-threatening. Paralytic shellfish poisoning, neurotoxic shellfish poisoning and amnesic shellfish poisoning are the most common immediate diseases that occur in individuals who consume tainted seafood.

The effects of cyanobacteria in seafood are currently being studied, and researchers are investigating the possible link between consumption of seafood tainted with this bacteria and the development of ALS (commonly known as Lou Gehrig’s disease). Scientists also suspect that seafood contaminated with these bacteria may also play a role in the development of Alzheimer’s disease, Parkinson’s disease and other neurological disorders in some individuals.

PCB’s are known carcinogens that were banned in America in 1976 because of their cancer-causing abilities. They are at the top of the current, dirty dozen list of toxic chemicals.

Dioxins are believed to be one of the worst toxins found in seafood. A known carcinogen, dioxins are known to cause cancer, impairment of the immune system, birth defects, endocrine disorders and learning disabilities.

Is There Treatment for Toxic Seafood Diseases

Once a diagnosis of marine toxin poisoning is confirmed, treatment can begin. Diagnosis requires an evaluation of symptoms together with a recent history of seafood consumption. Occasionally, laboratory tests will be required to check for the presence of specific toxins in the blood. Leftover pieces of seafood can also be tested for the presence of the toxin.

For shellfish poisoning, the only type of treatment currently available is supportive care to ease symptoms and speed recovery. The use of antihistamines and epinephrine can help control allergic-type reactions for certain types of shellfish poisoning.

How Common Are Toxic Seafood Diseases

An estimated 30 cases of seafood poisoning as a result of marine toxins are reported annually in the United States. The number of actual cases is likely much higher, as health care providers are not required to report this type of illness. Additionally, individuals with mild cases may not seek medical treatment. There is currently no database to track the number of individuals suffering from long-term effects of seafood toxins such as cancer and other serious health conditions.

What Can You Do?

Any time seafood is consumed, there is a chance that the seafood may be contaminated with marine toxins. Any individual who consumes seafood has the risk of becoming ill due to eating toxic shellfish. Individuals who have a compromised immune system are more susceptible to shellfish poisoning. However, even individuals in good health should be concerned about the health risks associated with consuming seafood that contains high levels of toxins. General guidelines for decreasing your risk of consuming contaminated seafood include:

  • Place seafood on ice or keep it refrigerated to prevent spoilage
  • Refrain from eating barracuda
  • Watch for health advisories issued by local government officials about toxic seafood
  • Refrain from eating shellfish that is sold as bait
  • Inform your local public health department if you or anyone in your family becomes ill as a result of seafood poisoning or marine toxins


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