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Mercury Levels in Fish & Animals

Mercury is a toxic substance that exists naturally but has also been introduced into some areas via pollution from mining or industrial activities, according to the U.S. Geological Survey (USGS). Mercury levels in fish and animals in these locations can build up and cause health problems.

  1. Methylmercury

    • Methylmercury is the main form of organic mercury encountered by fish and other animals, according to the U.S. Environmental Protection Agency (EPA). Exposure to this highly toxic form of mercury typically occurs through ingestion.

    Animals

    • Methylmercury damages the immune, enzyme and genetic systems within animals. The nervous system is also affected, with coordination and the senses often damaged. Mercury levels are often highest in animals such as fish-eating birds, according to the USGS.

    Fish

    • Methylmercury enters the aquatic food chain quickly, according to the U.S. EPA. Entrance into the food chain is typically through absorption of methylmercury into plants and small organisms which are then consumed by the fish.

    Embryos

    • Embryos are 5 to 10 times more sensitive to methylmercury than adult animals and exposure often causes deformities, plus neurological and reproductive issues, according to the USGS.

    Sources

    • Pollution is one source of mercury in animals and fish and, in some locations, is the major source of this substance, according to the USGS. However, most high-mercury areas appear to be due to natural causes such as an increase in atmospheric deposition, when mercury is deposited from the air. Atmospheric sources of mercury include volcanic action and mercury deposits found naturally in rocks.

    Warning

    • Animals and fish containing mercury are generally considered safe for human consumption in amounts of 10 grams of affected animals or less per day (with mercury concentrations of (.1 to .15 parts per million), according to the the EPA's 1997 Mercury Study Report to Congress. Women of childbearing age who are or may become pregnant should be especially careful to adhere to these guidelines.

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