Learn · Contaminants Science

Contaminants in Seafood: What the Science Says

Mercury, PCBs, microplastics — the concerns are real, but the risk is species- and origin-specific. For Alaska wild-caught seafood, the nutritional benefits substantially outweigh documented risks.

The Context That Usually Gets Left Out

Media coverage of seafood contaminants tends toward alarm without context. The relevant question is never “does this fish contain mercury?” — all fish contain trace amounts of mercury. The question is whether levels in a specific species from a specific region pose a health risk relative to the nutritional benefits of eating seafood.

For most Americans, the answer is: the benefits substantially outweigh the risks for the species they're likely to eat. The meaningful contaminant concerns are real but narrow — concentrated in specific high-risk species that are easy to identify and avoid.

Alaska wild-caught seafood — salmon, halibut, sablefish, cod, crab — is consistently documented among the lowest-contaminant seafood available. The clean North Pacific, short food chains, and lack of industrial aquaculture feed all contribute.

Three Contaminants Explained

Mechanism, which species to watch, Alaska context, and current guidance.

Mercury

Bioaccumulation

High for specific species. Low for Alaska wild-caught.

How It Works

Mercury enters the ocean primarily from industrial emissions. Bacteria convert it to methylmercury, which accumulates in fish tissue. Large, long-lived predatory fish at the top of the food chain concentrate mercury from everything they eat — a process called biomagnification.

Higher Risk

•Shark
•Swordfish
•King mackerel
•Tilefish (Gulf of Mexico)
•Bigeye tuna

Lower Risk

•Alaska salmon (all species)
•Alaska halibut
•Alaska sablefish
•Shrimp
•Cod
•Pollock

Alaska Context

Alaska salmon, halibut, and sablefish are consistently among the lowest mercury seafood available. The cold, clean North Pacific and relatively short food chains for salmon keep mercury levels well below any concern threshold. FDA and EPA advisory levels for mercury apply to high-risk species — not to Alaska wild-caught fish.

FDA / Current Guidance

FDA/EPA advise pregnant women and young children to avoid shark, swordfish, king mackerel, and tilefish. They recommend 2–3 servings per week of lower-mercury choices, explicitly including salmon, cod, and pollock.

PCBs

Persistent Organic Pollutants (POPs)

Relevant for farmed fish. Low for Alaska wild-caught.

How It Works

Polychlorinated biphenyls were industrial chemicals used through the 1970s before being banned. They persist in the environment, accumulate in fatty tissue, and build up through the food chain. Farmed salmon have historically shown higher PCB levels than wild because they are fed fish meal and fish oil produced from forage fish — concentrating the pollutants.

Higher Risk

•Farmed Atlantic salmon (historically)
•Fish from heavily industrialized coastal areas

Lower Risk

•Wild Alaska salmon
•Wild Alaska halibut
•Wild Pacific species generally

Alaska Context

Studies comparing wild Alaska salmon to farmed Atlantic salmon have found wild Alaska salmon to have significantly lower PCB levels — often 5–10x lower. The North Pacific feed chain is less contaminated, and wild salmon do not receive concentrated feed. Alaska wild-caught seafood is among the lowest PCB options in the market.

FDA / Current Guidance

The FDA does not issue specific PCB advisories for wild Alaska salmon. Some state advisories exist for farmed salmon. The Monterey Bay Aquarium's testing has confirmed wild Alaska salmon PCB levels are well within safe thresholds.

Microplastics

Emerging contaminant

Most relevant for whole shellfish. Ongoing research for finfish.

How It Works

Plastic particles smaller than 5mm have been found throughout the ocean. Filter-feeding shellfish (mussels, oysters, clams) concentrate microplastics because they filter large volumes of water to feed. Finfish in open ocean have lower documented exposure, though research is ongoing.

Higher Risk

•Mussels
•Oysters
•Clams and other bivalves (consumed whole)

Lower Risk

•Wild pelagic finfish (open ocean)
•Halibut, salmon, sablefish

Alaska Context

Microplastic research in Alaska waters is ongoing. Studies to date show lower concentrations in remote North Pacific waters compared to coastal industrial zones. For finfish — where the digestive tract is removed before consumption — human exposure is further reduced. This is an area of active research, not a settled question.

FDA / Current Guidance

No current FDA guidelines specific to microplastics in seafood. WHO and FDA consider the evidence insufficient for specific consumption advisories at this time, while calling for continued research.

The Other Side of the Equation

Contaminant risk analysis is incomplete without accounting for nutritional benefits. For most species, this is not a close call.

Nutrient	Health Benefit	Best Sources
Omega-3 fatty acids	Cardiovascular health, brain function, anti-inflammatory	Salmon, sablefish, halibut
Protein	Lean, complete protein with all essential amino acids	All seafood species
Vitamin D	Bone health, immune function — deficient in most American diets	Salmon, sablefish, halibut
Selenium	Antioxidant, thyroid function, may counteract mercury toxicity	Salmon, halibut, cod, tuna
Iodine	Thyroid hormone production	Shrimp, cod, tuna
B12	Neurological function, red blood cell formation	Salmon, halibut, clams, tuna

The Bottom Line

The same principle that governs sustainability also governs contaminants: species + origin + method matter.

High-mercury fish are real and should be avoided by pregnant women and young children. They are: shark, swordfish, king mackerel, tilefish, and bigeye tuna. Alaska salmon, halibut, and sablefish are not on that list.

PCBs are a meaningful concern for farmed salmon raised on concentrated fish meal and fish oil. They are not a meaningful concern for wild Alaska salmon.

Microplastics research is ongoing. Current evidence suggests greatest exposure from whole shellfish. Finfish in open North Pacific waters are a low-concern category at current evidence levels.

Alaska wild-caught seafood is among the cleanest commercially available. The benefits of eating it — omega-3s, lean protein, selenium, vitamin D — substantially outweigh documented contaminant risks. The recommendation from FDA, EPA, and the Dietary Guidelines is clear: eat more seafood, not less, with attention to high-mercury species.

Species Guide →Farmed vs. Wild Buying Guide