Microplastics in Seafood: Which Fish Are Safest to Eat?

Introduction: The Hidden Cost of Seafood

Seafood has long been celebrated as one of the healthiest protein sources available. Rich in omega-3 fatty acids, lean protein, vitamins, and minerals, fish and shellfish are staples of heart-healthy and brain-boosting diets worldwide. But in recent years, a growing body of scientific research has revealed an uncomfortable reality: the oceans that produce our seafood are also repositories for millions of tons of plastic waste, and that plastic is making its way onto our plates.

An estimated eight million metric tons of plastic enter the world's oceans every year. Over time, sunlight, wave action, and salt water break this plastic down into microplastics, particles smaller than five millimeters, and even smaller nanoplastics that measure less than one micrometer. These particles are now so pervasive in marine environments that researchers have detected them in every ocean basin, from Arctic ice to deep-sea sediments. Marine organisms ingest these particles at every level of the food chain, from microscopic plankton to the largest whales.

For seafood lovers, this raises urgent questions. Which fish and shellfish contain the most microplastics? Are some species safer than others? Does it matter whether your fish is wild-caught or farmed? This guide examines the latest research to help you make informed choices about the seafood you eat while still enjoying its considerable nutritional benefits. For a broader look at how microplastics contaminate our diets, see our comprehensive guide on microplastics in food.

How Microplastics Enter the Marine Food Chain

Understanding how microplastics move through the ocean ecosystem is essential to understanding why certain seafood species are more contaminated than others. The journey begins with plastic debris entering waterways through rivers, stormwater runoff, wastewater treatment plants, and direct dumping. Once in the ocean, larger plastic items gradually fragment into smaller and smaller pieces through photodegradation and mechanical weathering.

At the base of the marine food chain, phytoplankton and zooplankton encounter these microplastic particles suspended in the water column. Studies have shown that zooplankton readily ingest microplastics, mistaking them for food due to their similar size. Small fish and filter-feeding organisms like mussels and oysters then consume both the contaminated plankton and free-floating microplastics directly from the water. As larger predators eat smaller organisms, microplastics accumulate up the food chain in a process known as trophic transfer.

Filter-feeding organisms are particularly vulnerable because their feeding mechanism involves processing enormous volumes of water to extract nutrients. A single mussel can filter up to twenty-five liters of water per day, concentrating any microplastics present in that water within its tissues. This is why shellfish consistently rank among the most microplastic-laden seafood categories in scientific studies.

Beyond ingestion, microplastics also adsorb persistent organic pollutants, heavy metals, and other toxic chemicals from seawater onto their surfaces. When a marine organism ingests a microplastic particle, it may also be ingesting a concentrated dose of these adsorbed contaminants, amplifying the potential health impact beyond the plastic itself. To learn more about these health implications, read our article on microplastics and health effects.

Which Seafood Has the Most Microplastics?

Not all seafood carries the same microplastic burden. The key factor is whether you eat the entire organism, including its digestive system, or only the muscle tissue (fillet). Organisms consumed whole tend to have dramatically higher microplastic counts because the gastrointestinal tract is where ingested plastics accumulate.

Mussels and Oysters: The Highest Risk

Bivalve mollusks like mussels, oysters, clams, and scallops consistently rank as the most microplastic-contaminated seafood. As filter feeders, they strain massive volumes of seawater through their bodies to extract food particles. Any microplastics suspended in that water become trapped in their tissues. Because we eat these organisms whole, including their digestive tract, gills, and soft tissues, we consume every microplastic particle they have accumulated.

Research published in Environmental Pollution found that mussels can contain anywhere from 0.2 to 7.2 microplastic particles per gram of tissue, depending on their growing environment. A typical serving of mussels weighing around two hundred grams could therefore contain up to 1,440 microplastic particles. Oysters show similar contamination levels, with studies finding an average of 0.5 to 5 particles per gram. Farmed mussels and oysters grown in coastal waters near urban areas or industrial zones tend to have the highest concentrations.

Shrimp and Prawns: A Close Second

Shrimp and prawns are among the most popular seafood items globally, and unfortunately, they also carry significant microplastic loads. While larger shrimp are often deveined and peeled before eating (which removes the digestive tract and reduces exposure somewhat), many preparations involve eating smaller shrimp whole. Even when deveined, microplastics can migrate from the gut into surrounding muscle tissue over time.

A 2020 study in Environmental Science & Technology found microplastics in 75 percent of shrimp samples tested from markets across multiple countries. The average concentration was approximately one to two particles per gram of shrimp tissue. Shrimp from heavily polluted coastal waters and intensive aquaculture farms showed the highest levels.

Small Fish Eaten Whole

Anchovies, sardines, and other small fish that are often consumed whole, including their intestines, represent another high-exposure category. A study in Marine Pollution Bulletin examined sardines and anchovies from the Mediterranean and found microplastics in the gastrointestinal tracts of over 50 percent of samples. When these fish are eaten whole, as they commonly are in many cuisines, all those accumulated particles are consumed. However, when sardines are filleted and the gut cavity is removed, the microplastic exposure drops significantly.

Fish That Are Relatively Safer

The encouraging news is that many popular fish species, when consumed as fillets, have considerably lower microplastic contamination. The crucial distinction is that filleting removes the gastrointestinal tract, gills, and other organs where microplastics primarily accumulate. The muscle tissue of most fish contains far fewer particles.

Filleted Fish: Lower Risk

When you eat a salmon fillet, a piece of cod, or a tuna steak, you are eating only the muscle tissue. Multiple studies have found that the microplastic concentration in fish muscle is significantly lower than in the viscera. Research published in Science of the Total Environment showed that while the gastrointestinal tract of fish may contain dozens of microplastic particles, the muscle tissue typically contains fewer than one particle per gram.

Species that tend to be lower in microplastics when consumed as fillets include:

1. Salmon (especially wild-caught Alaskan salmon), which lives in relatively clean, cold waters and is almost always consumed as fillets.
2. Cod and haddock, deep-water species that are typically filleted, removing the organs where microplastics concentrate.
3. Pollock, commonly used in fish sticks and fish sandwiches, always consumed as processed fillets with all organs removed.
4. Trout, particularly freshwater trout from clean mountain streams and lakes, tends to have lower microplastic exposure than coastal species.
5. Mahi-mahi and halibut, open-ocean species typically sold as thick fillets or steaks with all viscera removed during processing.

It is important to note that "safer" is a relative term. Even filleted fish are not microplastic-free. Nanoplastics, which are small enough to penetrate cell membranes, can migrate from the gut into muscle tissue and other organs. However, the concentrations in muscle tissue remain substantially lower than in whole organisms.

Wild-Caught vs Farmed Fish: Which Is Better?

The wild-versus-farmed debate is more nuanced than many people assume when it comes to microplastics. Neither category is universally better, and the answer often depends on the specific species, farming practices, and geographic location.

The Case for Wild-Caught

Wild fish living in open ocean environments generally encounter lower concentrations of microplastics compared to those in coastal or enclosed waters. Deep-sea species and those from remote, less-polluted regions like Alaska, the southern Pacific, and the open Atlantic tend to have among the lowest microplastic levels. Wild fish also eat a natural diet, which means their microplastic exposure comes solely from their environment and prey, not from manufactured feed.

The Case for Farmed Fish

Farmed fish present a mixed picture. On one hand, aquaculture operations in enclosed or controlled environments could theoretically produce fish with lower microplastic exposure if the water quality is carefully managed. Some land-based recirculating aquaculture systems (RAS) can filter water to remove particulates, potentially reducing microplastic intake.

On the other hand, many ocean-based fish farms are located in coastal waters that tend to have higher microplastic concentrations due to proximity to urban runoff, industrial discharge, and shipping lanes. Additionally, commercial fish feed pellets have been found to contain microplastics. A 2021 study in Aquaculture detected microplastic particles in multiple brands of commercial fish feed, meaning farmed fish may ingest microplastics from their feed as well as from the surrounding water.

The bottom line: the location and practices of the farm matter more than whether the fish is wild or farmed. When possible, look for fish from well-managed fisheries in clean waters, whether wild or farmed. Certifications like the Marine Stewardship Council (MSC) for wild fish and the Aquaculture Stewardship Council (ASC) for farmed fish can help guide your choices.

Geographic Differences in Seafood Contamination

Where your seafood comes from matters enormously. Microplastic concentrations in the ocean vary dramatically by region, and this directly affects the contamination levels in marine organisms harvested from those waters.

1. Highest contamination zones: The Mediterranean Sea, the South China Sea, and coastal waters near major Asian manufacturing hubs consistently show the highest microplastic concentrations. Seafood from these regions tends to carry the heaviest microplastic burdens. The Mediterranean is essentially a semi-enclosed basin surrounded by densely populated coastlines, trapping plastic pollution with limited exchange with the open Atlantic.
2. Moderate contamination zones: The North Atlantic, North Pacific, and coastal waters near major cities worldwide fall into a middle range. These areas are affected by ocean gyres that concentrate floating plastic debris, as well as by local pollution from coastal populations.
3. Lower contamination zones: Remote regions like the waters off Alaska, Norway, Iceland, New Zealand, and parts of the southern Pacific and southern Atlantic tend to have lower microplastic concentrations. Seafood from these areas, while not microplastic-free, generally has lower contamination levels.

When shopping for seafood, pay attention to country of origin labels. Seafood from northern, remote, or well-regulated fisheries tends to be a better choice from a microplastic perspective. Fish labeled as product of China, Vietnam, Thailand, or Indonesia may carry higher microplastic loads due to the generally higher contamination levels in surrounding waters, though this is a generalization and individual results can vary.

Shellfish vs Finfish: A Direct Comparison

When comparing broad categories of seafood, the distinction between shellfish and finfish is one of the most important factors in microplastic exposure.

Shellfish (mussels, oysters, clams, shrimp, crab, lobster) are generally higher in microplastics for several reasons. Bivalves are filter feeders that process huge volumes of water. Shrimp and crab live on or near the ocean floor where microplastics tend to settle and accumulate in sediment. Many shellfish are eaten whole or with minimal processing, meaning the digestive tract and its accumulated microplastics are consumed.

Finfish (salmon, cod, tuna, halibut, and similar species) are generally lower in microplastics when consumed as fillets. Their feeding mechanisms do not involve filtering water in the same way as bivalves. When properly filleted, the organs that accumulate the most microplastics are removed. The muscle tissue that we eat contains significantly fewer particles per gram compared to whole shellfish.

This does not mean you need to eliminate shellfish entirely. Rather, it means being strategic about how often you eat them and where they are sourced. Treating shellfish as an occasional delicacy rather than a daily staple, and choosing specimens from cleaner waters, can meaningfully reduce your overall microplastic intake from seafood.

Can Cooking Methods Help Reduce Microplastics?

Once microplastics are embedded in seafood tissue, no cooking method can fully eliminate them. However, certain preparation and cooking techniques may help reduce your exposure.

1. Remove the gut and organs. The single most effective step is to properly clean and gut your fish. Removing the head, digestive tract, gills, and internal organs eliminates the areas where microplastics are most concentrated. Even with small fish like sardines, taking the time to fillet and gut them rather than eating them whole can substantially reduce microplastic intake.
2. Rinse thoroughly. Rinsing fish fillets and shellfish under clean, filtered water before cooking can wash away surface microplastic particles. While this will not remove particles embedded in tissue, it can reduce surface contamination.
3. Boiling and discarding the water. When cooking shellfish like mussels or clams, boiling them and discarding the cooking liquid may remove some microplastics that leach out during cooking. However, research on this method is still limited.
4. Avoid adding more plastic during cooking. Use stainless steel, cast iron, or ceramic cookware rather than non-stick pans with plastic coatings. Do not wrap fish in plastic wrap before cooking. Use parchment paper or banana leaves instead of plastic bags for steaming or sous vide preparations.
5. Devein shrimp properly. The dark vein running along the back of a shrimp is actually its digestive tract. Removing this before cooking eliminates the area with the highest concentration of ingested microplastics. Always devein shrimp regardless of size.

Sustainable Seafood Choices That Also Minimize Microplastics

There is significant overlap between sustainable seafood practices and lower microplastic contamination. Fisheries and aquaculture operations that prioritize environmental stewardship tend to operate in cleaner waters and use practices that result in lower contamination levels.

1. Choose MSC or ASC certified seafood. These certifications indicate that the fishery or farm meets rigorous environmental standards. While the certifications do not directly measure microplastics, the practices they require tend to correlate with lower contamination.
2. Buy local when possible. Seafood from local, well-managed fisheries often has shorter supply chains, meaning less time for additional contamination through plastic packaging and processing. Local fishmongers can also tell you exactly where and how the fish was caught.
3. Prefer smaller, shorter-lived species. Smaller fish lower on the food chain have had less time and fewer trophic levels to accumulate microplastics. Sardines, mackerel, and herring (when filleted) are nutritionally excellent and tend to have lower contaminant loads than large, long-lived predators like swordfish or shark.
4. Consider the source waters. Alaskan wild salmon, Norwegian cod, and Icelandic haddock come from some of the cleanest fishing waters on Earth. These regions have strong environmental regulations and relatively low coastal populations, resulting in lower microplastic contamination.
5. Support companies reducing plastic in fishing gear. Ghost fishing nets and discarded gear are a major source of ocean microplastics. Companies and fisheries that actively collect and recycle old nets and gear are helping reduce the very pollution that contaminates seafood.

How Much Seafood Is Safe to Eat?

Despite the microplastic concern, most health organizations continue to recommend eating seafood two to three times per week due to its substantial nutritional benefits. The omega-3 fatty acids, high-quality protein, vitamin D, selenium, and other nutrients in fish provide health benefits that are well-documented and significant. The question is not whether to eat seafood, but how to eat it more strategically.

Based on current research, here is a practical framework for minimizing microplastic exposure while maintaining a healthy seafood intake:

1. Aim for two to three servings of filleted finfish per week. Focus on species like salmon, cod, trout, pollock, and halibut. These provide the nutritional benefits of seafood with lower microplastic exposure per serving compared to shellfish.
2. Limit shellfish to occasional consumption. Rather than eating mussels, oysters, or shrimp multiple times per week, treat them as an occasional indulgence. Once or twice a month is a reasonable frequency that lets you enjoy these foods without making them a primary protein source.
3. Vary your seafood selections. Eating a wide variety of fish from different sources helps ensure that you are not repeatedly exposed to the specific contaminants that may be concentrated in one species or region. Diversity in your seafood choices is a simple and effective risk-reduction strategy.
4. Balance seafood with other protein sources. Complement your seafood intake with plant-based proteins, pasture-raised poultry, and other minimally processed protein sources to reduce your overall reliance on any single category.
5. Pay extra attention for vulnerable populations. Pregnant women, nursing mothers, and young children should be particularly strategic about seafood choices. Favor low-mercury, low-microplastic options like wild Alaskan salmon and well-sourced cod. The omega-3 benefits are especially important during pregnancy and early development, but so is minimizing contaminant exposure.

Using the MicroPlastics App for Seafood Products

Making informed seafood choices at the grocery store or fish market can feel overwhelming when you are trying to balance nutritional benefits, sustainability, sourcing, and microplastic contamination. The MicroPlastics app simplifies this process by giving you instant, science-backed assessments of seafood products right at the point of purchase.

1. Scan packaged seafood products. Use the app to scan frozen fish fillets, canned tuna, smoked salmon, and other packaged seafood items. The app evaluates the product based on species, sourcing, processing methods, and packaging materials to give you a comprehensive microplastic risk score.
2. Compare different brands and sources. Not all salmon fillets are equal. The app lets you quickly compare options side by side, helping you choose the product with the lowest estimated microplastic risk from the options available at your store.
3. Track your seafood consumption over time. The app's tracking features help you monitor how much and what types of seafood you are eating, giving you insight into your overall exposure patterns and helping you maintain a balanced, lower-risk diet.
4. Stay updated on new research. The science of microplastics in seafood is rapidly evolving. The app incorporates the latest peer-reviewed findings into its assessments, so your decisions are always based on current evidence rather than outdated information.

Conclusion: Eat Smarter, Not Less

Microplastics in seafood are a real and growing concern, but they should not cause you to abandon one of the most nutritious food groups available. The health benefits of eating well-sourced seafood, including reduced cardiovascular risk, improved brain function, and essential nutrients that are difficult to obtain elsewhere, remain substantial and well-supported by decades of research.

The key is to be strategic. Choose filleted finfish over whole shellfish as your primary seafood. Source from clean, well-managed fisheries in northern or remote waters. Properly gut, clean, and prepare your fish to remove the organs where microplastics concentrate. Limit high-risk items like mussels, oysters, and whole shrimp to occasional treats rather than dietary staples. And use tools like the MicroPlastics app to make informed decisions at the point of purchase.

The ocean plastic crisis demands systemic solutions, including better waste management, reduced plastic production, and international cooperation. But while we work toward those long-term goals, individual choices about what seafood we buy and how we prepare it can meaningfully reduce our personal and our families' microplastic exposure today.

Download the MicroPlastics app today to start scanning your seafood products and making smarter choices for your health and the health of your family.