Microplastics in Sushi: Raw Fish, Soy Sauce Packets & Plastic Trays

Why raw fish concentrates microplastic

Fish ingest microplastic through their gills and digestive systems. Particles concentrate in the gut, gills, and to a lesser extent in muscle tissue. When fish is cooked, the gut is removed first, but raw preparations like sushi often use whole-fish cuts that preserve more of the microplastic load. Several factors compound:

• Large predator fish (bluefin tuna, swordfish, mackerel) bioaccumulate plastic alongside mercury.
• Wild-caught vs farmed matters less than people think, both contain measurable microplastic.
• Whole small fish (anchovies, sardines, ikura roe) include the gut, increasing particle load per gram.

See our parent article on microplastics in seafood for the broader picture.

The black plastic sushi tray problem

The 2024 Toxic-Free Future / Chemosphere study tested 203 black plastic consumer products. Sushi trays were among the worst, many tested positive for brominated flame retardants from recycled electronics waste. The black plastic is in direct contact with raw fish, rice, and seaweed for the entire shelf life from supermarket prep to your meal (sometimes 6-12 hours or more).

The fix: avoid black plastic trays. Restaurants serving on ceramic plates eliminate this entirely. Some upscale grocers (Whole Foods, Erewhon) use clear PET trays which are not flame-retardant-contaminated but still plastic-contact.

Fish-shaped soy sauce packets

Those iconic little fish-shaped soy sauce containers (called shoyu-tai) are typically made of polyethylene or, in some markets, PLA bioplastic. They sit in direct contact with concentrated soy sauce (a salty, somewhat acidic liquid) sometimes for months of shelf life. Microplastic and plasticiser release into the soy is not well-quantified but likely meaningful. Bring your own glass-bottled soy sauce when possible.

Sushi format ranked

Practical changes

1. Eat sushi at the restaurant rather than takeout when possible.
2. Choose smaller fish (salmon, mackerel, sardines) over large predators (bluefin tuna, swordfish) for both mercury and microplastic reasons.
3. Avoid black plastic trays entirely, ask for ceramic or compostable fibre containers.
4. Skip fish-shaped soy sauce packets, bring your own glass-bottled soy.
5. Don't microwave sushi trays, heat dramatically accelerates plastic leaching.
6. Make sushi at home with filleted fish from a glass tray and a bamboo rolling mat, full control.
7. Limit weekly sushi frequency if you eat it often, average 5g plastic / week guidance applies to high-frequency consumers.

See related: microplastics in seafood, microplastics in meat, and microplastics in fast food.