Microplastics in seafood, salt, and beer: a layperson's guide

Microplastics have been detected in nearly every food category that's been seriously tested. Here's what the studies actually found and what it means.

Sea salt

A landmark 2017 study published in Scientific Reports tested 16 sea salt brands from eight countries and found microplastic in 15 of 16. A subsequent 2018 study expanded the sample to 39 brands across 21 countries and found microplastic in 36 of 39 — the unaffected three were rock salt and well-purified table salt, not sea salt.

Estimated annual exposure: a typical adult consuming sea salt at recommended dietary levels would ingest roughly 2,000 microplastic particles per year from salt alone.

Bivalves (mussels, oysters, clams)

Bivalves filter-feed by drawing water through their bodies — which means they accumulate microplastic from the water they live in. Studies have found microplastic in 100% of commercial mussels tested in some markets, with concentrations of 0.5–3 microplastic particles per mussel.

Because we eat the entire bivalve (digestive tract included), this is one of the few seafood categories where consumed microplastic is measurable per serving.

Fish and crustaceans

Microplastic has been detected in the digestive tracts of most studied wild-caught fish species. The good news for human consumers: we typically don't eat the digestive tract. The microplastic that ends up in human-consumed fish flesh is much lower — concentrations are detectable but small.

Crustaceans (shrimp, crab, lobster) sit somewhere in between — some microplastic in flesh, more in body parts not typically consumed.

Beer

A 2014 study in Food Additives & Contaminants tested 24 German beers and found microplastic fibers in all 24, plus fragments in many. A 2018 study of U.S. craft beers found microplastic in 12 of 12 tested, with brews from the Great Lakes region showing the highest concentrations (likely from contaminated brewing water).

Tea bags

Plastic tea bags release microplastic when steeped. A 2019 McGill University study found that a single nylon or PET tea bag releases ~11.6 billion microplastic particles and 3.1 billion nanoplastic particles into a 95°C cup of water. Paper tea bags don't have this problem.

Honey, sugar, fresh produce

Less-studied but where data exists, similar findings: microplastic detected in most samples. Atmospheric deposition (microplastic falling from the air as dust) is the proposed primary contamination source.

Total dietary exposure

A 2019 study in Environmental Science & Technology attempted a comprehensive estimate of human microplastic ingestion across diet, drinking water, and air. The estimated total: roughly 5 grams of microplastic per week — about a credit card's worth — for an average adult.

This estimate has been pushed back on (some studies find lower, some higher) but it became widely cited. The order-of-magnitude finding is what matters: not zero, not trivial, real but not yet linked to specific human health outcomes.

What the health data says

As covered in our piece on microplastics in drinking water, peer-reviewed evidence on human health effects of dietary microplastic exposure remains preliminary. Animal studies show inflammation and endocrine effects at higher doses; human studies have detected microplastic in tissues but not yet established causal health outcomes.

The honest framing: we are running an uncontrolled experiment on the global food supply. The results may turn out to be benign or substantial; we don't yet know.

What you can do

• Choose paper tea bags over plastic.
• Glass storage containers for leftovers, especially hot food.
• Don't microwave food in plastic.
• If you're a heavy bivalve consumer, be aware of source water quality.
• Reduce plastic in your own life. The microplastics in food in 2050 are the plastics being thrown away in 2026.