How much mercury is in the fish you eat, and is it dangerous?
Depends on the species. Large predatory fish (tuna, swordfish, shark) have high mercury. Smaller fish (sardines, salmon, shrimp) are much safer.
What's actually in it
Mercury gets into fish from industrial pollution in water. Small fish absorb it. Bigger fish eat the small fish and concentrate the mercury in their tissues. The bigger and older the fish, the more mercury it carries.
The main concern is methylmercury, the organic form that accumulates in fish. It crosses the blood-brain barrier and the placenta. It's a neurotoxin.
What the research says
A 2025 study in Science of the Total Environment analyzed mercury levels across fish species using 10 years of data (2011-2021). The findings confirmed longstanding patterns and revealed some new ones.
Shark, swordfish, king mackerel, and bigeye tuna consistently had the highest mercury concentrations. Canned albacore tuna was in the moderate range. Canned light tuna (mostly skipjack) was lower but not zero.
Salmon, sardines, anchovies, herring, shrimp, and tilapia all had very low mercury levels. They're the fish you can eat regularly without concern.
The FDA recommends that pregnant women and young children avoid high-mercury fish entirely. For everyone else, eating high-mercury fish more than once a week is where risk starts accumulating. Mercury stays in your body for months.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Mercury levels and trends in fish (2011-2021): A Bayesian approach with multi-group analysis | Science of the Total Environment | 2025 |
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