Mercury in fish

Mercury in fish is the presence of mercury compounds in fish tissue, chiefly methylmercury, which can expose people who eat fish.

Methylmercury: An organic mercury compound formed mainly by microbes in aquatic environments and readily accumulated by organisms. It is the mercury compound responsible for most exposure from eating fish.
Fish consumption advisories: Public notices recommending limits or restrictions on eating fish from particular waters or species. Advisories communicate when mercury levels make particular catches risky to eat.
Methylmercury poisoning: Illness caused by exposure to methylmercury, which can damage the nervous system. Eating heavily contaminated fish can cause toxic exposure and neurological harm.
Inorganic mercury: Mercury compounds lacking carbon–mercury bonds, including mercuric salts. It behaves differently from methylmercury, which dominates mercury exposure from fish.
Bioaccumulation: The buildup of a substance in an organism when uptake exceeds elimination. Fish accumulate mercury from food and water faster than they can eliminate it.
Pregnancy and mercury exposure: The concern that methylmercury exposure during pregnancy can harm fetal brain development. Dietary guidance often focuses on protecting fetal development while preserving fish’s nutritional benefits.
Minamata disease: A neurological disease caused by severe methylmercury poisoning in Minamata, Japan. The outbreak demonstrated how industrial mercury contamination can reach people through seafood.
Elemental mercury: Mercury in its pure metallic form, which is liquid at room temperature. Elemental mercury is not the principal mercury form found in fish tissue.
Biomagnification: The increase in a contaminant’s concentration across successive levels of a food chain. Predatory fish often contain more methylmercury because it concentrates up the aquatic food web.
Fish testing for mercury: Laboratory measurement of mercury concentrations in fish tissue. Tissue testing provides the data used to assess risk and issue consumption guidance.

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