What is Mercury and why should you be concerned?
Mercury is a chemical element on the periodic table with the symbol Hg. It is highly toxic in both its liquid and gaseous forms. If ingested or inhaled it can cause brain, liver, and central nervous system damage. It is bioacumulative and is easily absorbed through the skin. When exposed to high amounts over long periods of time death can occur. When working in a lab it should be used under a well- ventilated hood. In the natural environment Mercury ingestion can be minimized by eating aquatic foods lower on the food chain.
Global Cycle of Mercury
The global cycle of mercury includes a combination of anthropogenic sources (industrial combustion, mining) and natural sources (ocean soils) which introduces mercury into water sources. As mercury enters the aquatic environment it is consumed by small organisms which are consumed by more predatory species further concentrating the levels of mercury toxicity.
Conversion of Mercury into Methyl Mercury
Methyl mercury is mercury’s most toxic form. It affects the immune system, alters genetic systems and damages the nervous system. It is particularly toxic to developing embryos. Mercury becomes methyl mercury through oxidation of Hg (0) to Hg (II) and 2 transformations from Hg (II) to CH3HG+ (methylation)
Bioaccumulation and Biomagnification of Methyl Mercury in Aquatic Food Chains
Mercury biomagnifies from the bottom to the top of the food chain.
For example, if an anchovy eats 10 plankton contaminated with 10 mg of Hg the anchovy would have accumulated 100 mg of Hg. If a catfish eats 5 anchovies it would have accumulated 500 mg of Hg. If a King Mackerel eats 4 cat fish it would have accumulated 20,000 mg of Hg. If a human eats 2 King Mackerel it would consume 40,000 mg of Hg as opposed to 1,000 mg from eating 2 catfish.
Concentrations of Concern in Freshwater fish
Regulations Regarding Human Consumption
The FDA has 3 recommendations for selecting and eating fish
- Do not eat predatory fish high in mercury
- Eat up to 12 ounces a week of a variety of fish and shellfish that are lower in mercury.
- Check local advisories about the safety of fish caught by family and friends at your local water sources
Mechanism of Toxicity
As mentioned earlier, toxicity increases through bioaccumulation and biomagnification. However, toxicity will decline if an individual stops eating fish or eats fish with lower concentrations of mercury. In humans, about half the body burden of mercury can be eliminated in 70 days if no mercury is ingested during that time
Mercury in the environment
Mercury in Dorena Lake
Mercury Tuna version of Mc Donald's Supersize me experiment
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