Dr. Jeff Hersh

Q:  How does mercury get into fish, and how much fish is safe to eat?

A:  There are many nutrients we need to get in order to stay healthy, including some metals (for example we need iron to make the hemoglobin that carries oxygen in our red blood cells). However, mercury is NOT needed for humans, and this heavy metal can cause toxicity and health problems (mercury poisoning), including neuropsychological disorders (for example tremors, emotional instability, insomnia, memory loss, others), kidney problems and/or thyroid issues, among other health issues. 

Where does the mercury come from in the first place? Like most elements (that is, all elements except the specifically man-made ones), mercury occurs naturally in nature.  Humans then foolishly increase airborne mercury by industrial activity like coal-fired electricity generation, smelting, burning of certain wastes, and others. 

Mercury in its elemental form (just mercury, Hg, itself) is the only metal which is liquid at room temperature, and is used to make thermometers, to purify gold or silver, to make fluorescent lamps and for other industrial uses. Historically it was (mis)used to make certain red dyes and for other purposes. Elemental mercury is poorly absorbed (0.01%) if ingested.

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